Americium

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Americium,  ₉₅Am

Americium
Pronunciation	/ˌæmɪˈrɪsiəm/ ​(AM-ə-RISS-ee-əm)
Appearance	silvery white
Mass number	243 (most stable isotope)
Americium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Eu ↑ Am ↓ (Uqe) plutonium ← americium → curium
Atomic number (Z)	95
Group	group n/a
Period	period 7
Block	f-block
Element category	actinide
Electron configuration	[Rn] 5f7 7s2
Electrons per shell	2, 8, 18, 32, 25, 8, 2
Physical properties
Phase at STP	solid
Melting point	1449 K ​(1176 °C, ​2149 °F)
Boiling point	2880 K ​(2607 °C, ​4725 °F) (calculated)
Density (near r.t.)	12 g/cm3
Heat of fusion	14.39 kJ/mol
Molar heat capacity	62.7 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1239 1356
Atomic properties
Oxidation states	+2, +3, +4, +5, +6, +7 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.3
Ionization energies	1st: 578 kJ/mol
Atomic radius	empirical: 173 pm
Covalent radius	180±6 pm
Spectral lines of americium
Other properties
Natural occurrence	synthetic
Crystal structure	​double hexagonal close-packed (dhcp)
Thermal conductivity	10 W/(m·K)
Electrical resistivity	0.69 µΩ·m
Magnetic ordering	paramagnetic
Magnetic susceptibility	+1000.0·10−6 cm3/mol
CAS Number	7440-35-9
History
Naming	after the Americas
Discovery	Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso (1944)
Main isotopes of americium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 241Am syn 432.2 y SF – α 237Np 242m1Am syn 141 y IT 242Am α 238Np SF – 243Am syn 7370 y SF – α 239Np

Americium is a synthetic chemical element with symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium, and thus by analogy was named after the Americas.

Americium was first produced in 1944 by the group of Glenn T. Seaborg from Berkeley, California, at the Metallurgical Laboratory of the University of Chicago, a part of the Manhattan Project. Although it is the third element in the transuranic series, it was discovered fourth, after the heavier curium. The discovery was kept secret and only released to the public in November 1945. Most americium is produced by uranium or plutonium being bombarded with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains about 100 grams of americium. It is widely used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Several unusual applications, such as nuclear batteries or fuel for space ships with nuclear propulsion, have been proposed for the isotope ^242mAm, but they are as yet hindered by the scarcity and high price of this nuclear isomer.

Americium is a relatively soft radioactive metal with silvery appearance. Its common isotopes are ²⁴¹Am and ²⁴³Am. In chemical compounds, americium usually assumes the oxidation state +3, especially in solutions. Several other oxidation states are known, which range from +2 to +7 and can be identified by their characteristic optical absorption spectra. The crystal lattice of solid americium and its compounds contain small intrinsic radiogenic defects, due to metamictization induced by self-irradiation with alpha particles, which accumulates with time; this can cause a drift of some material properties over time, more noticeable in older samples.

History

The 60-inch cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley, in August 1939.

 

The triangle in the glass tube contains the first sample of americium (as the hydroxide (Am(OH)₃)), produced in 1944.

 

Although americium was likely produced in previous nuclear experiments, it was first intentionally synthesized, isolated and identified in late autumn 1944, at the University of California, Berkeley, by Glenn T. Seaborg, Leon O. Morgan, Ralph A. James, and Albert Ghiorso. They used a 60-inch cyclotron at the University of California, Berkeley. The element was chemically identified at the Metallurgical Laboratory (now Argonne National Laboratory) of the University of Chicago. Following the lighter neptunium, plutonium, and heavier curium, americium was the fourth transuranium element to be discovered. At the time, the periodic table had been restructured by Seaborg to its present layout, containing the actinide row below the lanthanide one. This led to americium being located right below its twin lanthanide element europium; it was thus by analogy named after the Americas: "The name americium (after the Americas) and the symbol Am are suggested for the element on the basis of its position as the sixth member of the actinide rare-earth series, analogous to europium, Eu, of the lanthanide series."

The new element was isolated from its oxides in a complex, multi-step process. First plutonium-239 nitrate (²³⁹PuNO₃) solution was coated on a platinum foil of about 0.5 cm² area, the solution was evaporated and the residue was converted into plutonium dioxide (PuO₂) by calcining. After cyclotron irradiation, the coating was dissolved with nitric acid, and then precipitated as the hydroxide using concentrated aqueous ammonia solution. The residue was dissolved in perchloric acid. Further separation was carried out by ion exchange, yielding a certain isotope of curium. The separation of curium and americium was so painstaking that those elements were initially called by the Berkeley group as pandemonium (from Greek for all demons or hell) and delirium (from Latin for madness).

Initial experiments yielded four americium isotopes: ²⁴¹Am, ²⁴²Am, ²³⁹Am and ²³⁸Am. Americium-241 was directly obtained from plutonium upon absorption of two neutrons. It decays by emission of a α-particle to ²³⁷Np; the half-life of this decay was first determined as 510±20 years but then corrected to 432.2 years.

${\displaystyle {\ce {^{239}_{94}Pu ->[{\ce {(n,\gamma)}}] ^{240}_{94}Pu ->[{\ce {(n,\gamma)}}] ^{241}_{94}Pu ->[\beta^-][14.35\ {\ce {yr}}] ^{241}_{95}Am}}\ \left({\ce {->[\alpha][432.2\ {\ce {yr}}] ^{237}_{93}Np}}\right)}$

The times are half-lives

The second isotope ²⁴²Am was produced upon neutron bombardment of the already-created ²⁴¹Am. Upon rapid β-decay, ²⁴²Am converts into the isotope of curium ²⁴²Cm (which had been discovered previously). The half-life of this decay was initially determined at 17 hours, which was close to the presently accepted value of 16.02 h.

${\displaystyle {\ce {^{241}_{95}Am ->[{\ce {(n,\gamma)}}] ^{242}_{95}Am}}\ \left({\ce {->[\beta^-][16.02\ {\ce {h}}] ^{242}_{96}Cm}}\right)}$

The discovery of americium and curium in 1944 was closely related to the Manhattan Project; the results were confidential and declassified only in 1945. Seaborg leaked the synthesis of the elements 95 and 96 on the U.S. radio show for children Quiz Kids five days before the official presentation at an American Chemical Society meeting on 11 November 1945, when one of the listeners asked whether any new transuranium element beside plutonium and neptunium had been discovered during the war. After the discovery of americium isotopes ²⁴¹Am and ²⁴²Am, their production and compounds were patented listing only Seaborg as the inventor. The initial americium samples weighed a few micrograms; they were barely visible and were identified by their radioactivity. The first substantial amounts of metallic americium weighing 40–200 micrograms were not prepared until 1951 by reduction of americium(III) fluoride with barium metal in high vacuum at 1100 °C.

Occurrence

Americium was detected in the fallout from the Ivy Mike nuclear test.

 

The longest-lived and most common isotopes of americium, ²⁴¹Am and ²⁴³Am, have half-lives of 432.2 and 7,370 years, respectively. Therefore, any primordial americium (americium that was present on Earth during its formation) should have decayed by now.

Existing americium is concentrated in the areas used for the atmospheric nuclear weapons tests conducted between 1945 and 1980, as well as at the sites of nuclear incidents, such as the Chernobyl disaster. For example, the analysis of the debris at the testing site of the first U.S. hydrogen bomb, Ivy Mike, (1 November 1952, Enewetak Atoll), revealed high concentrations of various actinides including americium; but due to military secrecy, this result was not published until later, in 1956. Trinitite, the glassy residue left on the desert floor near Alamogordo, New Mexico, after the plutonium-based Trinity nuclear bomb test on 16 July 1945, contains traces of americium-241. Elevated levels of americium were also detected at the crash site of a US Boeing B-52 bomber aircraft, which carried four hydrogen bombs, in 1968 in Greenland.

In other regions, the average radioactivity of surface soil due to residual americium is only about 0.01 picocuries/g (0.37 mBq/g). Atmospheric americium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 1,900 times higher concentration of americium inside sandy soil particles than in the water present in the soil pores; an even higher ratio was measured in loam soils.

Americium is produced mostly artificially in small quantities, for research purposes. A tonne of spent nuclear fuel contains about 100 grams of various americium isotopes, mostly ²⁴¹Am and ²⁴³Am. Their prolonged radioactivity is undesirable for the disposal, and therefore americium, together with other long-lived actinides, must be neutralized. The associated procedure may involve several steps, where americium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure is well known as nuclear transmutation, but it is still being developed for americium. The transuranic elements from americium to fermium occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so.

Synthesis and extraction

Isotope nucleosyntheses

Chromatographic elution curves revealing the similarity between the lanthanides Tb, Gd, and Eu and the corresponding actinides Bk, Cm, and Am.

 

Americium has been produced in small quantities in nuclear reactors for decades, and kilograms of its ²⁴¹Am and ²⁴³Am isotopes have been accumulated by now. Nevertheless, since it was first offered for sale in 1962, its price, about 1,500 USD per gram of ²⁴¹Am, remains almost unchanged owing to the very complex separation procedure. The heavier isotope ²⁴³Am is produced in much smaller amounts; it is thus more difficult to separate, resulting in a higher cost of the order 100,000–160,000 USD/g.

Americium is not synthesized directly from uranium – the most common reactor material – but from the plutonium isotope ²³⁹Pu. The latter needs to be produced first, according to the following nuclear process:

${\displaystyle {\ce {^{238}_{92}U ->[{\ce {(n,\gamma)}}] ^{239}_{92}U ->[\beta^-][23.5 \ {\ce {min}}] ^{239}_{93}Np ->[\beta^-][2.3565 \ {\ce {d}}] ^{239}_{94}Pu}}}$

The capture of two neutrons by ²³⁹Pu (a so-called (n,γ) reaction), followed by a β-decay, results in ²⁴¹Am:

${\displaystyle {\ce {^{239}_{94}Pu ->[{\ce {2(n,\gamma)}}] ^{241}_{94}Pu ->[\beta^-][14.35 \ {\ce {yr}}] ^{241}_{95}Am}}}$

The plutonium present in spent nuclear fuel contains about 12% of ²⁴¹Pu. Because it spontaneously converts to ²⁴¹Am, ²⁴¹Pu can be extracted and may be used to generate further ²⁴¹Am. However, this process is rather slow: half of the original amount of ²⁴¹Pu decays to ²⁴¹Am after about 15 years, and the ²⁴¹Am amount reaches a maximum after 70 years.

The obtained ²⁴¹Am can be used for generating heavier americium isotopes by further neutron capture inside a nuclear reactor. In a light water reactor (LWR), 79% of ²⁴¹Am converts to ²⁴²Am and 10% to its nuclear isomer ^242mAm:

${\displaystyle {\begin{cases}79\%:&{\ce {^{241}_{95}Am ->[{\ce {(n,\gamma)}}] ^{242}_{95}Am}}\\10\%:&{\ce {^{241}_{95}Am ->[{\ce {(n,\gamma)}}] ^{242 m}_{95}Am}}\end{cases}}}$

Americium-242 has a half-life of only 16 hours, which makes its further conversion to ²⁴³Am extremely inefficient. The latter isotope is produced instead in a process where ²³⁹Pu captures four neutrons under high neutron flux:

${\displaystyle {\ce {^{239}_{94}Pu ->[{\ce {4(n,\gamma)}}] \ ^{243}_{94}Pu ->[\beta^-][4.956 \ {\ce {h}}] ^{243}_{95}Am}}}$

Metal generation

Most synthesis routines yield a mixture of different actinide isotopes in oxide forms, from which isotopes of americium can be separated. In a typical procedure, the spent reactor fuel (e.g. MOX fuel) is dissolved in nitric acid, and the bulk of uranium and plutonium is removed using a PUREX-type extraction (Plutonium–URanium EXtraction) with tributyl phosphate in a hydrocarbon. The lanthanides and remaining actinides are then separated from the aqueous residue (raffinate) by a diamide-based extraction, to give, after stripping, a mixture of trivalent actinides and lanthanides. Americium compounds are then selectively extracted using multi-step chromatographic and centrifugation techniques with an appropriate reagent. A large amount of work has been done on the solvent extraction of americium. For example, a 2003 EU-funded project codenamed "EUROPART" studied triazines and other compounds as potential extraction agents. A bis-triazinyl bipyridine complex was proposed in 2009 as such a reagent is highly selective to americium (and curium). Separation of americium from the highly similar curium can be achieved by treating a slurry of their hydroxides in aqueous sodium bicarbonate with ozone, at elevated temperatures. Both Am and Cm are mostly present in solutions in the +3 valence state; whereas curium remains unchanged, americium oxidizes to soluble Am(IV) complexes which can be washed away.

Metallic americium is obtained by reduction from its compounds. Americium(III) fluoride was first used for this purpose. The reaction was conducted using elemental barium as reducing agent in a water- and oxygen-free environment inside an apparatus made of tantalum and tungsten.

${\displaystyle \mathrm {2\ AmF_{3}\ +\ 3\ Ba\ \longrightarrow \ 2\ Am\ +\ 3\ BaF_{2}} }$

An alternative is the reduction of americium dioxide by metallic lanthanum or thorium:

${\displaystyle \mathrm {3\ AmO_{2}\ +\ 4\ La\ \longrightarrow \ 3\ Am\ +\ 2\ La_{2}O_{3}} }$

Physical properties

Double-hexagonal close packing with the layer sequence ABAC in the crystal structure of α-americium (A: green, B: blue, C: red).

 

In the periodic table, americium is located to the right of plutonium, to the left of curium, and below the lanthanide europium, with which it shares many similarities in physical and chemical properties. Americium is a highly radioactive element. When freshly prepared, it has a silvery-white metallic lustre, but then slowly tarnishes in air. With a density of 12 g/cm³, americium is less dense than both curium (13.52 g/cm³) and plutonium (19.8 g/cm³); but has a higher density than europium (5.264 g/cm³)—mostly because of its higher atomic mass. Americium is relatively soft and easily deformable and has a significantly lower bulk modulus than the actinides before it: Th, Pa, U, Np and Pu. Its melting point of 1173 °C is significantly higher than that of plutonium (639 °C) and europium (826 °C), but lower than for curium (1340 °C).

At ambient conditions, americium is present in its most stable α form which has a hexagonal crystal symmetry, and a space group P6₃/mmc with cell parameters a = 346.8 pm and c = 1124 pm, and four atoms per unit cell. The crystal consists of a double-hexagonal close packing with the layer sequence ABAC and so is isotypic with α-lanthanum and several actinides such as α-curium. The crystal structure of americium changes with pressure and temperature. When compressed at room temperature to 5 GPa, α-Am transforms to the β modification, which has a face-centered cubic (fcc) symmetry, space group Fm3m and lattice constant a = 489 pm. This fcc structure is equivalent to the closest packing with the sequence ABC. Upon further compression to 23 GPa, americium transforms to an orthorhombic γ-Am structure similar to that of α-uranium. There are no further transitions observed up to 52 GPa, except for an appearance of a monoclinic phase at pressures between 10 and 15 GPa. There is no consistency on the status of this phase in the literature, which also sometimes lists the α, β and γ phases as I, II and III. The β-γ transition is accompanied by a 6% decrease in the crystal volume; although theory also predicts a significant volume change for the α-β transition, it is not observed experimentally. The pressure of the α-β transition decreases with increasing temperature, and when α-americium is heated at ambient pressure, at 770 °C it changes into an fcc phase which is different from β-Am, and at 1075 °C it converts to a body-centered cubic structure. The pressure-temperature phase diagram of americium is thus rather similar to those of lanthanum, praseodymium and neodymium.

As with many other actinides, self-damage of the crystal structure due to alpha-particle irradiation is intrinsic to americium. It is especially noticeable at low temperatures, where the mobility of the produced structure defects is relatively low, by broadening of X-ray diffraction peaks. This effect makes somewhat uncertain the temperature of americium and some of its properties, such as electrical resistivity. So for americium-241, the resistivity at 4.2 K increases with time from about 2 µOhm·cm to 10 µOhm·cm after 40 hours, and saturates at about 16 µOhm·cm after 140 hours. This effect is less pronounced at room temperature, due to annihilation of radiation defects; also heating to room temperature the sample which was kept for hours at low temperatures restores its resistivity. In fresh samples, the resistivity gradually increases with temperature from about 2 µOhm·cm at liquid helium to 69 µOhm·cm at room temperature; this behavior is similar to that of neptunium, uranium, thorium and protactinium, but is different from plutonium and curium which show a rapid rise up to 60 K followed by saturation. The room temperature value for americium is lower than that of neptunium, plutonium and curium, but higher than for uranium, thorium and protactinium.

Americium is paramagnetic in a wide temperature range, from that of liquid helium, to room temperature and above. This behavior is markedly different from that of its neighbor curium which exhibits antiferromagnetic transition at 52 K. The thermal expansion coefficient of americium is slightly anisotropic and amounts to (7.5±0.2)×10⁻⁶ /°C along the shorter a axis and (6.2±0.4)×10⁻⁶ /°C for the longer c hexagonal axis. The enthalpy of dissolution of americium metal in hydrochloric acid at standard conditions is −620.6±1.3 kJ/mol, from which the standard enthalpy change of formation (Δ_fH°) of aqueous Am³⁺ ion is −621.2±2.0 kJ/mol. The standard potential Am³⁺/Am⁰ is −2.08±0.01 V.

Chemical properties

Americium ions in solution: Am³⁺ (left) and Am⁴⁺ (right). Am³⁺ is colorless at low and reddish at higher concentrations.

 

Americium readily reacts with oxygen and dissolves well in acids. The most common oxidation state for americium is +3, in which americium compounds are rather stable against oxidation and reduction. In this sense, americium is chemically similar to most lanthanides. The trivalent americium forms insoluble fluoride, oxalate, iodate, hydroxide, phosphate and other salts. Other oxidation states have been observed between +2 and +7, which is the widest range among the actinide elements. Their color in aqueous solutions varies as follows: Am³⁺ (colorless to yellow-reddish), Am⁴⁺ (yellow-reddish), Am^VO⁺
₂; (yellow), Am^VIO²⁺
₂ (brown) and Am^VIIO⁵⁻
₆ (dark green). All oxidation states have their characteristic optical absorption spectra, with a few sharp peaks in the visible and mid-infrared regions, and the position and intensity of these peaks can be converted into the concentrations of the corresponding oxidation states. For example, Am(III) has two sharp peaks at 504 and 811 nm, Am(V) at 514 and 715 nm, and Am(VI) at 666 and 992 nm. 

Americium compounds with oxidation state +4 and higher are strong oxidizing agents, comparable in strength to the permanganate ion (MnO⁻
₄) in acidic solutions. Whereas the Am⁴⁺ ions are unstable in solutions and readily convert to Am³⁺, the +4 oxidation state occurs well in solids, such as americium dioxide (AmO₂) and americium(IV) fluoride (AmF₄). 

All pentavalent and hexavalent americium compounds are complex salts such as KAmO₂F₂, Li₃AmO₄ and Li₆AmO₆, Ba₃AmO₆, AmO₂F₂. These high oxidation states Am(IV), Am(V) and Am(VI) can be prepared from Am(III) by oxidation with ammonium persulfate in dilute nitric acid, with silver(I) oxide in perchloric acid, or with ozone or sodium persulfate in sodium carbonate solutions. The pentavalent oxidation state of americium was first observed in 1951. It is present in aqueous solution in the form of AmO⁺
₂ ions (acidic) or AmO⁻
₃ ions (alkaline) which are however unstable and subject to several rapid disproportionation reactions:

${\displaystyle {\ce {3AmO2+ + 4H+ -> 2AmO2^2+ + Am^3+ + 2H2O}}}$

${\displaystyle {\ce {2Am^{V}-> Am^{VI}{}+ Am^{IV}}}}$

Chemical compounds

Oxygen compounds

Three americium oxides are known, with the oxidation states +2 (AmO), +3 (Am₂O₃) and +4 (AmO₂). Americium(II) oxide was prepared in minute amounts and has not been characterized in details. Americium(III) oxide is a red-brown solid with a melting point of 2205 °C. Americium(IV) oxide is the main form of solid americium which is used in nearly all its applications. As most other actinide dioxides, it is a black solid with a cubic (fluorite) crystal structure.

The oxalate of americium(III), vacuum dried at room temperature, has the chemical formula Am₂(C₂O₄)₃·7H₂O. Upon heating in vacuum, it loses water at 240 °C and starts decomposing into AmO₂ at 300 °C, the decomposition completes at about 470 °C. The initial oxalate dissolves in nitric acid with the maximum solubility of 0.25 g/L.

Halides

Halides of americium are known for the oxidation states +2, +3 and +4,^[63] where the +3 is most stable, especially in solutions.

Oxidation state	F	Cl	Br	I
+4	Americium(IV) fluoride AmF4 pale pink
+3	Americium(III) fluoride AmF3 pink	Americium(III) chloride AmCl3 pink	Americium(III) bromide AmBr3 light yellow	Americium(III) iodide AmI3 light yellow
+2		Americium(II) chloride AmCl2 black	Americium(II) bromide AmBr2 black	Americium(II) iodide AmI2 black

Reduction of Am(III) compounds with sodium amalgam yields Am(II) salts – the black halides AmCl₂, AmBr₂ and AmI₂. They are very sensitive to oxygen and oxidize in water, releasing hydrogen and converting back to the Am(III) state. Specific lattice constants are:

• Orthorhombic AmCl₂: a = 896.3±0.8 pm, b = 757.3±0.8 pm and c = 453.2±0.6 pm
• Tetragonal AmBr₂: a = 1159.2±0.4 pm and c = 712.1±0.3 pm. They can also be prepared by reacting metallic americium with an appropriate mercury halide HgX₂, where X = Cl, Br or I:

${\displaystyle {\ce {{Am}+{\underset {mercury\ halide}{HgX2}}->[{} \atop 400-500^{\circ }{\ce {C}}]{AmX2}+{Hg}}}}$

Americium(III) fluoride (AmF₃) is poorly soluble and precipitates upon reaction of Am³⁺ and fluoride ions in weak acidic solutions:

${\displaystyle {\ce {Am^3+ + 3F^- -> AmF3(v)}}}$

The tetravalent americium(IV) fluoride (AmF₄) is obtained by reacting solid americium(III) fluoride with molecular fluorine:

${\displaystyle {\ce {2AmF3 + F2 -> 2AmF4}}}$

Another known form of solid tetravalent americium chloride is KAmF₅. Tetravalent americium has also been observed in the aqueous phase. For this purpose, black Am(OH)₄ was dissolved in 15-M NH₄F with the americium concentration of 0.01 M. The resulting reddish solution had a characteristic optical absorption spectrum which is similar to that of AmF₄ but differed from other oxidation states of americium. Heating the Am(IV) solution to 90 °C did not result in its disproportionation or reduction, however a slow reduction was observed to Am(III) and assigned to self-irradiation of americium by alpha particles.

Most americium(III) halides form hexagonal crystals with slight variation of the color and exact structure between the halogens. So, chloride (AmCl₃) is reddish and has a structure isotypic to uranium(III) chloride (space group P6₃/m) and the melting point of 715 °C. The fluoride is isotypic to LaF₃ (space group P6₃/mmc) and the iodide to BiI₃ (space group R3). The bromide is an exception with the orthorhombic PuBr₃-type structure and space group Cmcm. Crystals of americium hexahydrate (AmCl₃·6H₂O) can be prepared by dissolving americium dioxide in hydrochloric acid and evaporating the liquid. Those crystals are hygroscopic and have yellow-reddish color and a monoclinic crystal structure.

Oxyhalides of americium in the form Am^VIO₂X₂, Am^VO₂X, Am^IVOX₂ and Am^IIIOX can be obtained by reacting the corresponding americium halide with oxygen or Sb₂O₃, and AmOCl can also be produced by vapor phase hydrolysis:

${\displaystyle {\ce {AmCl3 + H2O -> AmOCl + 2HCl}}}$

Chalcogenides and pnictides

The known chalcogenides of americium include the sulfide AmS₂, selenides AmSe₂ and Am₃Se₄, and tellurides Am₂Te₃ and AmTe₂. The pnictides of americium (²⁴³Am) of the AmX type are known for the elements phosphorus, arsenic, antimony and bismuth. They crystallize in the rock-salt lattice.

Silicides and borides

Americium monosilicide (AmSi) and "disilicide" (nominally AmSi_x with: 1.87 < x < 2.0) were obtained by reduction of americium(III) fluoride with elementary silicon in vacuum at 1050 °C (AmSi) and 1150−1200 °C (AmSi_x). AmSi is a black solid isomorphic with LaSi, it has an orthorhombic crystal symmetry. AmSi_x has a bright silvery lustre and a tetragonal crystal lattice (space group I4₁/amd), it is isomorphic with PuSi₂ and ThSi₂. Borides of americium include AmB₄ and AmB₆. The tetraboride can be obtained by heating an oxide or halide of americium with magnesium diboride in vacuum or inert atmosphere.

Organoamericium compounds

Predicted structure of amerocene [(η⁸-C₈H₈)₂Am]

 

Analogous to uranocene, americium forms the organometallic compound amerocene with two cyclooctatetraene ligands, with the chemical formula (η⁸-C₈H₈)₂Am. A cyclopentadienyl complex is also known that is likely to be stoichiometrically AmCp₃.

Formation of the complexes of the type Am(n-C₃H₇-BTP)₃, where BTP stands for 2,6-di(1,2,4-triazin-3-yl)pyridine, in solutions containing n-C₃H₇-BTP and Am³⁺ ions has been confirmed by EXAFS. Some of these BTP-type complexes selectively interact with americium and therefore are useful in its selective separation from lanthanides and another actinides.

Biological aspects

Americium is an artificial element of recent origin, and thus does not have a biological requirement. It is harmful to life. It has been proposed to use bacteria for removal of americium and other heavy metals from rivers and streams. Thus, Enterobacteriaceae of the genus Citrobacter precipitate americium ions from aqueous solutions, binding them into a metal-phosphate complex at their cell walls. Several studies have been reported on the biosorption and bioaccumulation of americium by bacteria and fungi.

Fission

The isotope ^242mAm (half-life 141 years) has the largest cross sections for absorption of thermal neutrons (5,700 barns), that results in a small critical mass for a sustained nuclear chain reaction. The critical mass for a bare ^242mAm sphere is about 9–14 kg (the uncertainty results from insufficient knowledge of its material properties). It can be lowered to 3–5 kg with a metal reflector and should become even smaller with a water reflector. Such small critical mass is favorable for portable nuclear weapons, but those based on ^242mAm are not known yet, probably because of its scarcity and high price. The critical masses of two other readily available isotopes, ²⁴¹Am and ²⁴³Am, are relatively high – 57.6 to 75.6 kg for ²⁴¹Am and 209 kg for ²⁴³Am. Scarcity and high price yet hinder application of americium as a nuclear fuel in nuclear reactors.

There are proposals of very compact 10-kW high-flux reactors using as little as 20 grams of ^242mAm. Such low-power reactors would be relatively safe to use as neutron sources for radiation therapy in hospitals.

Isotopes

About 19 isotopes and 8 nuclear isomers are known for americium. There are two long-lived alpha-emitters; ²⁴³Am has a half-life of 7,370 years and is the most stable isotope, and ²⁴¹Am has a half-life of 432.2 years. The most stable nuclear isomer is ^242m1Am; it has a long half-life of 141 years. The half-lives of other isotopes and isomers range from 0.64 microseconds for ^245m1Am to 50.8 hours for ²⁴⁰Am. As with most other actinides, the isotopes of americium with odd number of neutrons have relatively high rate of nuclear fission and low critical mass.

Americium-241 decays to ²³⁷Np emitting alpha particles of 5 different energies, mostly at 5.486 MeV (85.2%) and 5.443 MeV (12.8%). Because many of the resulting states are metastable, they also emit gamma rays with the discrete energies between 26.3 and 158.5 keV.

Americium-242 is a short-lived isotope with a half-life of 16.02 h. It mostly (82.7%) converts by β-decay to ²⁴²Cm, but also by electron capture to ²⁴²Pu (17.3%). Both ²⁴²Cm and ²⁴²Pu transform via nearly the same decay chain through ²³⁸Pu down to ²³⁴U. 

Nearly all (99.541%) of ^242m1Am decays by internal conversion to ²⁴²Am and the remaining 0.459% by α-decay to ²³⁸Np. The latter subsequently decays to ²³⁸Pu and then to ²³⁴U.

Americium-243 transforms by α-emission into ²³⁹Np, which converts by β-decay to ²³⁹Pu, and the ²³⁹Pu changes into ²³⁵U by emitting an α-particle.

Applications

Outside and inside view of an americium-based smoke detector

Ionization-type smoke detector

Americium is used in the most common type of household smoke detector, which uses ²⁴¹Am in the form of americium dioxide as its source of ionizing radiation. This isotope is preferred over ²²⁶Ra because it emits 5 times more alpha particles and relatively little harmful gamma radiation. Element collector Theodore Gray mentions in his book The Elements: A Visual Exploration of Every Known Atom in the Universe:

You might think that a synthetic radioactive element that follows plutonium (94)—and has a significantly shorter half-life—would be some kind of superbomb material, available only to scientists in secret laboratories. Perhaps a mad scientist is studying americium in a lair somewhere, but if you want some yourself you can simply walk into any neighborhood hardware store, supermarket, or Wal-Mart and buy some, no questions asked.

The reason is not that americium is fundamentally less dangerous than the elements around it. In fact, the commonly available isotope, ²⁴¹Am, is significantly more radioactive than weapons-grade plutonium, and at least as toxic. No, the difference is simply that there is a useful application for americium that requires only a very tiny amount, and for which a company was prepared to go through the effort required to carve out and get a regulatory exception.

The amount of americium in a typical new smoke detector is 1 microcurie (37 kBq) or 0.29 microgram. This amount declines slowly as the americium decays into neptunium-237, a different transuranic element with a much longer half-life (about 2.14 million years). With its half-life of 432.2 years, the americium in a smoke detector includes about 3% neptunium after 19 years, and about 5% after 32 years. The radiation passes through an ionization chamber, an air-filled space between two electrodes, and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and affects this current, triggering the alarm. Compared to the alternative optical smoke detector, the ionization smoke detector is cheaper and can detect particles which are too small to produce significant light scattering; however, it is more prone to false alarms.

Radionuclide

As ²⁴¹Am has a roughly similar half-life to ²³⁸Pu (432.2 years vs. 87 years), it has been proposed as an active element of radioisotope thermoelectric generators, for example in spacecraft. Although americium produces less heat and electricity – the power yield is 114.7 mW/g for ²⁴¹Am and 6.31 mW/g for ²⁴³Am (cf. 390 mW/g for ²³⁸Pu) – and its radiation poses more threat to humans owing to neutron emission, the European Space Agency is considering using americium for its space probes.

Another proposed space-related application of americium is a fuel for space ships with nuclear propulsion. It relies on the very high rate of nuclear fission of ^242mAm, which can be maintained even in a micrometer-thick foil. Small thickness avoids the problem of self-absorption of emitted radiation. This problem is pertinent to uranium or plutonium rods, in which only surface layers provide alpha-particles. The fission products of ^242mAm can either directly propel the spaceship or they can heat a thrusting gas. They can also transfer their energy to a fluid and generate electricity through a magnetohydrodynamic generator.

One more proposal which utilizes the high nuclear fission rate of ^242mAm is a nuclear battery. Its design relies not on the energy of the emitted by americium alpha particles, but on their charge, that is the americium acts as the self-sustaining "cathode". A single 3.2 kg ^242mAm charge of such battery could provide about 140 kW of power over a period of 80 days. Even with all the potential benefits, the current applications of ^242mAm are as yet hindered by the scarcity and high price of this particular nuclear isomer.

Neutron source

The oxide of ²⁴¹Am pressed with beryllium is an efficient neutron source. Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:

${\displaystyle {\ce {^{241}_{95}Am -> ^{237}_{93}Np + ^{4}_{2}He + \gamma}}}$

${\displaystyle {\ce {^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}C + ^{1}_{0}n + \gamma}}}$

The most widespread use of ²⁴¹AmBe neutron sources is a neutron probe – a device used to measure the quantity of water present in soil, as well as moisture/density for quality control in highway construction. ²⁴¹Am neutron sources are also used in well logging applications, as well as in neutron radiography, tomography and other radiochemical investigations.

Production of other elements

Americium is a starting material for the production of other transuranic elements and transactinides – for example, 82.7% of ²⁴²Am decays to ²⁴²Cm and 17.3% to ²⁴²Pu. In the nuclear reactor, ²⁴²Am is also up-converted by neutron capture to ²⁴³Am and ²⁴⁴Am, which transforms by β-decay to ²⁴⁴Cm:

${\displaystyle {\ce {^{243}_{95}Am ->[{\ce {(n,\gamma)}}] ^{244}_{95}Am ->[\beta^-][10.1 \ {\ce {h}}] ^{244}_{96}Cm}}}$

Irradiation of ²⁴¹Am by ¹²C or ²²Ne ions yields the isotopes ²⁴⁷Es (einsteinium) or ²⁶⁰Db (dubnium), respectively. Furthermore, the element berkelium (²⁴³Bk isotope) had been first intentionally produced and identified by bombarding ²⁴¹Am with alpha particles, in 1949, by the same Berkeley group, using the same 60-inch cyclotron. Similarly, nobelium was produced at the Joint Institute for Nuclear Research, Dubna, Russia, in 1965 in several reactions, one of which included irradiation of ²⁴³Am with ¹⁵N ions. Besides, one of the synthesis reactions for lawrencium, discovered by scientists at Berkeley and Dubna, included bombardment of ²⁴³Am with ¹⁸O.

Spectrometer

Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. The 59.5409 keV gamma ray emissions from ²⁴¹Am in such sources can be used for indirect analysis of materials in radiography and X-ray fluorescence spectroscopy, as well as for quality control in fixed nuclear density gauges and nuclear densometers. For example, the element has been employed to gauge glass thickness to help create flat glass. Americium-241 is also suitable for calibration of gamma-ray spectrometers in the low-energy range, since its spectrum consists of nearly a single peak and negligible Compton continuum (at least three orders of magnitude lower intensity). Americium-241 gamma rays were also used to provide passive diagnosis of thyroid function. This medical application is however obsolete.

Health concerns

As a highly radioactive element, americium and its compounds must be handled only in an appropriate laboratory under special arrangements. Although most americium isotopes predominantly emit alpha particles which can be blocked by thin layers of common materials, many of the daughter products emit gamma-rays and neutrons which have a long penetration depth.

If consumed, most of the americium is excreted within a few days, with only 0.05% absorbed in the blood, of which roughly 45% goes to the liver and 45% to the bones, and the remaining 10% is excreted. The uptake to the liver depends on the individual and increases with age. In the bones, americium is first deposited over cortical and trabecular surfaces and slowly redistributes over the bone with time. The biological half-life of ²⁴¹Am is 50 years in the bones and 20 years in the liver, whereas in the gonads (testicles and ovaries) it remains permanently; in all these organs, americium promotes formation of cancer cells as a result of its radioactivity.

Americium often enters landfills from discarded smoke detectors. The rules associated with the disposal of smoke detectors are relaxed in most jurisdictions. In 1994, 17-year-old David Hahn extracted the americium from about 100 smoke detectors in an attempt to build a breeder nuclear reactor. There have been a few cases of exposure to americium, the worst case being that of chemical operations technician Harold McCluskey, who at the age of 64 was exposed to 500 times the occupational standard for americium-241 as a result of an explosion in his lab. McCluskey died at the age of 75 of unrelated pre-existing disease.

Breakthrough Starshot

From Wikipedia, the free encyclopedia

On 24 August 2016, ESO hosted a press conference to discuss the announcement of exoplanet Proxima b at its headquarters in Germany. In this picture, Pete Worden giving a speech.

 

Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft named StarChip, to be capable of making the journey to the Alpha Centauri star system 4.37 light-years away. 

A flyby mission has been proposed to Proxima Centauri b, an Earth-sized exoplanet in the habitable zone of its host star, Proxima Centauri, in the Alpha Centauri system. At a speed between 15% and 20% of the speed of light, it would take between twenty and thirty years to complete the journey, and approximately four years for a return message from the starship to Earth. 

The conceptual principles to enable this interstellar travel project were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara. Sending the lightweight spacecraft involves a multi-kilometer phased array of beam-steerable lasers with a combined coherent power output of up to 100 GW.

General

The project was announced on 12 April 2016 in an event held in New York City by physicist and venture capitalist Yuri Milner, together with cosmologist Stephen Hawking, who was serving as board member of the initiatives. Other board members include Facebook CEO Mark Zuckerberg. The project has an initial funding of US$100 million to initialize research. Milner places the final mission cost at $5–10 billion, and estimates the first craft could launch by around 2036. Pete Worden is the project's executive director and Professor Avi Loeb (Harvard University) chairs the Advisory Board for the project.

In 2017 Stephen Hawking told the audience at Starmus Festival:

Our physical resources are being drained at an alarming rate. We have given our planet the disastrous gift of climate change. Rising temperatures, reduction of the polar ice caps, deforestation and decimation of animal species. We can be an ignorant, unthinking lot. We are running out of space and the only places to go to are other worlds. It is time to explore other solar systems. Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth.

Leaders

Management and Advisory Committee:

• Pete Worden, Executive Director, Breakthrough Starshot; former Director of NASA Ames Research Center
• Avi Loeb, Chairman, Breakthrough Starshot Advisory Committee; Harvard University
• Jim Benford, Microwave Sciences
• Steven Chu, Nobel Prize winner, Stanford University
• Bruce Draine, Princeton University
• Ann Druyan, Cosmos Studios
• Freeman Dyson, Princeton Institute of Advanced Study
• Lou Friedman, Planetary Society, JPL
• Robert Fugate, Arctelum, LLC, New Mexico Tech
• Giancarlo Genta, Polytechnic University of Turin
• Olivier Guyon, University of Arizona
• Mae Jemison, 100 Year Starship
• Joan Johnson-Freese, US Naval War College
• Pete Klupar, Director of Engineering, Breakthrough Starshot; former Director of Engineering, NASA Ames Research Center
• Jeff Kuhn, University of Hawaii Institute for Astronomy
• Geoff Landis, SA Glenn Research Center
• Kelvin Long, Journal of the British Interplanetary Society
• Greg Matloff, New York City College of Technology
• Claire Max, University of California, Santa Cruz
• Kaya Nobuyuki, Kobe University
• Kevin Parkin, Parkin Research
• Mason Peck, Cornell University
• Saul Perlmutter, Nobel Prize winner, Breakthrough Prize winner, UC Berkeley and Lawrence Berkeley National Laboratory
• Martin Rees, Astronomer Royal
• Roald Sagdeev, University of Maryland
• Ed Turner, Princeton University, NAOJ

Objectives

The Breakthrough Starshot program aims to demonstrate a proof-of-concept for ultra-fast, light-driven nano-spacecraft, and lay the foundations for a first launch to Alpha Centauri within the next generation. Secondary goals are: Solar System exploration and detection of Earth-crossing asteroids. The spacecraft would make a flyby of, and, possibly photograph any Earth-like worlds that might exist in the system.

Target planet

In August 2016, the European Southern Observatory (ESO) announced the detection of a planet orbiting the third star in the Alpha Centauri system, Proxima Centauri. The planet, called Proxima Centauri b, is orbiting within the habitable zone of its star, and it could be a potential target for one of the projects of Breakthrough Initiatives. 

In January 2017, Breakthrough Initiatives and the European Southern Observatory entered a collaboration to search for habitable planets in the nearby star system, Alpha Centauri. The agreement involves Breakthrough Initiatives providing funding for an upgrade to the VISIR (VLT Imager and Spectrometer for mid-Infrared) instrument on ESO's Very Large Telescope (VLT) in Chile. This upgrade will greatly increase the likelihood of planet detection in the system.

Concept

A solar sail concept

 

The Starshot concept envisions launching a "mothership" carrying about a thousand tiny spacecraft (on the scale of centimeters) to a high-altitude Earth orbit and then deploying them. A phased array of ground-based lasers would then focus a light beam on the crafts' sails to accelerate them one by one to the target speed within 10 minutes, with an average acceleration on the order of 100 km/s² (10,000  ɡ), and an illumination energy on the order of 1 TJ delivered to each sail. A preliminary sail model is suggested to have a surface area of 4 m × 4 m. An October 2017 presentation of the Starshot system model examines circular sails and finds that the beam director capital cost is minimized by having a sail diameter of 5 meters.

Earth-size planet Proxima Centauri b was discovered in 2016 orbiting within the Alpha Centauri system habitable zones, compelling the Breakthrough Starshot to try to aim its spacecraft within 1 astronomical unit (150 million kilometers or 93 million miles) of it. From this distance, a craft's cameras could potentially capture an image of high enough quality to resolve surface features.

The fleet would have about 1000 spacecraft, and each one (dubbed a StarChip), would be a very small centimeter-sized vehicle weighing a few grams. They would be propelled by a square-kilometre array of 10 kW ground-based lasers with a combined output of up to 100 GW. A swarm of about 1000 units would compensate for the losses caused by interstellar dust collisions en route to the target. In a detailed study in 2016 Thiem Hoang and coworkers found that mitigating the collisions with dust, hydrogen and galactic cosmic rays may not be quite as severe an engineering problem as first thought.

Technical challenges

Light propulsion requires enormous power: a laser with a gigawatt of power (approximately the output of a large nuclear plant) would provide only a few newtons of thrust. The spaceship will compensate for the low thrust by having a mass of only a few grams. The camera, computer, communications laser, a plutonium power source, and the solar sail must be miniaturized to fit within a mass limit. All components must be engineered to endure extreme acceleration, cold, vacuum, and protons. The spacecraft will have to survive collisions with space dust; Starshot expects each square centimeter of frontal cross-section to collide at high speed with about a thousand particles of size at least 0.1 μm. Focusing a set of lasers totaling one hundred gigawatts onto the solar sail will be difficult due to atmospheric turbulence, so there is the suggestion to use space-based laser infrastructure. According to The Economist, at least a dozen off-the-shelf technologies will need to improve by orders of magnitude.

StarChip

StarChip is the name used by Breakthrough Initiatives for a very small, centimeter-sized, gram-scale, interstellar spacecraft envisioned for the Breakthrough Starshot program, a proposed mission to propel a fleet of a thousand StarChips on a journey to the Alpha Centauri star system, the nearest extrasolar stars, about 4.37 light-years from Earth. The journey may include a flyby of Proxima Centauri b, an Earth-sized exoplanet that is in the habitable zone of its host star. The ultra-light StarChip robotic nanocraft, fitted with lightsails, are planned to travel at speeds of 20% and 15% of the speed of light, taking between 20 and 30 years to reach the star system, respectively, and about 4 years to notify Earth of a successful arrival. The conceptual principles to enable practical interstellar travel were described in "A Roadmap to Interstellar Flight", by Philip Lubin of UC Santa Barbara, who is an advisor for the Starshot project.

In July 2017, scientists announced that precursors to StarChip, named Sprites, were successfully launched and flown through Polar Satellite Launch Vehicle by ISRO from Satish Dhawan Space Centre. Sprites will also be flown on the KickSat-2 mission scheduled for November 2018.

Components

Each StarChip nanocraft is expected to carry miniaturized cameras, navigation gear, communication equipment, photon thrusters and a power supply. In addition, each nanocraft would be fitted with a meter-scale lightsail, made of lightweight materials, with a gram-scale mass.

Cameras

Four sub-gram scale digital cameras, each with a minimum 2-megapixels resolution, are envisioned.

Processors

Four sub-gram scale processors are planned.

Photon thrusters

Four sub-gram scale photon thrusters, each minimally capable of performing at a 1W diode laser level, are planned.

Battery

A 150 mg atomic battery, powered by plutonium-238 or americium-241, is planned.

Protective coating

A coating, possibly made of beryllium copper, is planned to protect the nanocraft from dust collisions and atomic particle erosion.

Lightsail

The lightsail is envisioned to be no larger than 4 by 4 meters (13 by 13 feet), possibly of composite graphene-based material. The material would have to be very thin and be able to reflect the laser beam while absorbing only a small fraction of the incident energy, or it will vaporize the sail.

Other potential destinations

The table below lists possible target stars for similar photogravitational assist travel. The travel times are for the spacecraft to travel to the star and then enter orbit around the star (using photon pressure in maneuvers similar to aerobraking). 

Name	Travel time (yr)	Distance (ly)	Luminosity (L☉)
Proxima Centauri	121	4.2	0.00005
α Centauri A	101.25	4.36	1.52
α Centauri B	147.58	4.36	0.50
Sirius A	68.90	8.58	24.20
Procyon A	154.06	11.44	6.94
Vega	167.39	25.02	50.05
Altair	176.67	16.69	10.70
Fomalhaut A	221.33	25.13	16.67
Denebola	325.56	35.78	14.66
Castor A	341.35	50.98	49.85
Epsilon Eridani	363.35	10.50	0.50

• Successive assists at α Cen A and B could allow travel times to 75 yr to both stars.
• Lightsail has a nominal mass-to-surface ratio (σ_nom) of 8.6×10⁻⁴ gram m⁻² for a nominal graphene-class sail.
• Area of the Lightsail, about 10⁵ m² = (316 m)²
• Velocity up to 37,300 km s⁻¹ (12.5% c)

Other applications

The German physicist Claudius Gros has proposed that the technology of the Breakthrough Starshot initiative may be utilized in a second step to establish a biosphere of unicellular microbes on otherwise only transiently habitable exoplanets. A Genesis probe would travel at lower speeds, about 0.3% of the speed of light. It could hence be decelerated using a magnetic sail.

Islam and secularism

From Wikipedia, the free encyclopedia

The role of Islam or religion in the Muslim-majority countries as outlined in the constitutions, including Islamic and secular states

  Islamic state

  State religion

  Unclear / No declaration

  Secular state

Secularism has been a controversial concept in Islamic political thought, owing in part to historical factors and in part to the ambiguity of the concept itself. In the Muslim world, the notion has acquired strong negative connotations due to its association with removal of Islamic influences from the legal and political spheres under foreign colonial domination, as well as attempts to restrict public religious expression by some secularist nation states. Thus, secularism has often been perceived as a foreign ideology imposed by invaders and perpetuated by post-colonial ruling elites, and understood as equivalent to irreligion or antireligion.

Some Islamic reformists like Ali Abdel Raziq and Mahmoud Mohammed Taha have advocated a secular state in the sense of political order that does not impose any single interpretation of sharia on the nation. A number of Islamic and academic authors have argued that there is no religious reason that would prevent Muslims from accepting secularism in the sense of state neutrality toward religion. Abdullahi Ahmed An-Na'im has argued that a secular state built on constitutionalism, human rights and full citizenship is more consistent with Islamic history than modern visions of an Islamic state. Proponents of Islamism (political Islam) reject secularist views that would limit Islam to matters of personal belief and instead advocate for a return to Islamic law and Islamic political authority.

A number of pre-modern polities in the Islamic world demonstrated some level of separation between religious and political authority, even if they did not adhere to the modern concept of a state with no official religion or religion-based laws. Today, some Muslim-majority countries define themselves as or are regarded as secular, and many of them have a dual system in which Muslims can bring familial and financial disputes to sharia courts. The exact jurisdiction of these courts varies from country to country, but usually includes marriage, divorce, inheritance, and guardianship.

Definition

Secularism is an ambiguous concept that could be understood to refer to anticlericalism, atheism, state neutrality toward religion, the separation of religion from state, banishment of religious symbols from the public sphere, or disestablishment (separation of church and state), although the latter meaning would not be relevant in the Islamic context, since Islam has no institution corresponding to this sense of "church".

There is no word in Arabic, Persian or Turkish corresponding exactly to the English term "secularism". In Arabic, two words are commonly used as translations: ʿilmānīyah (from the Arabic word for science) and ʿalmanīyah. The latter term, which first appeared at the end of the nineteenth century in the dictionary Muhit al-Muhit written by the Christian Lebanese scholar Butrus al-Bustani, was apparently derived from the Arabic word for "world". Arab activists concerned about marginalization of religious practices and beliefs have sometimes used the term la diniyah (non-religion). In Persian, one finds the loan word sekularizm, while in Turkish laiklik comes from the French laïcité.

Overview

The concept of secularism was imported along with many of the ideas of post-enlightenment modernity from Europe into the Muslim world, namely Middle East and North Africa. Among Muslim intellectuals, the early debate on secularism centered mainly on the relationship between religion and state, and how this relationship was related to European successes in science, technology and governance. In the debate on the relationship between religion and state, (in)separability of religious and political authorities in the Islamic world, or status of the Caliph, was one of the biggest issues.

John L. Esposito, a professor of international affairs and Islamic studies, points out: "the post-independent period witnessed the emergence of modern Muslim states whose pattern of development was heavily influenced by and indebted to Western secular paradigms or models. Saudi Arabia and Turkey reflected the two polar positions. [...] The majority of Muslim states chose a middle ground in nation building, borrowing heavily from the West and relying on foreign advisers and Western-educated elites."

Esposito also argues that in many modern Muslim countries the role of Islam in state and society as a source of legitimation for rulers, state, and government institutions was greatly decreased though the separation of religion and politics was not total. However while most Muslim governments replaced Islamic law with legal systems inspired by western secular codes, Muslim family law (marriage, divorce, and inheritance) remained in force.

However, many Muslims argue that, unlike Christianity, Islam does not separate religion from the state and many Muslims around the world welcome a significant role for Islam in their countries' political life. It is apolitical Islam, not political Islam, that requires explanation and that is an historical fluke of the "shortlived heyday of secular Arab nationalism between 1945 and 1970."

Furthermore, the resurgence of Islam, beginning with the Iranian revolution of 1978-9, defied the illusions of advocates of secularization theory. The resurgence of Islam in politics in the most modernizing of Muslim countries, such as Egypt, Algeria and Turkey, betrayed expectations of those who believed religion should be at the margins not the center of public life. Furthermore, in most cases, it was not rural but urban phenomena, and its leaders and supporters were educated professionals.

From a more historical perspective, scholar Olivier Roy argues that "a defacto separation between political power" of sultans and emirs and religious power of the caliph was "created and institutionalized ... as early as the end of the first century of the hegira" and what has been lacking in the Muslim world is "political thought regarding the autonomy of this space." No positive law was developed outside of sharia. The sovereign's religious function was to defend the Islamic community against its enemies, institute the sharia, ensure the public good (maslaha). The state was an instrument to enable Muslims to live as good Muslims and Muslims were to obey the sultan if he did so. The legitimacy of the ruler was "symbolized by the right to coin money and to have the Friday prayer (Jumu'ah khutba) said in his name."

History

Early history

Ira M. Lapidus, an Emeritus Professor of Middle Eastern and Islamic History at The University of California at Berkeley, notes that religious and political power was united while the Prophet Muhammad was leading the ummah, resulting in a non-secular state. But Lapidus states that by the 10th century, some governments in the Muslim world had developed an effective separation of religion and politics, due to political control passing "into the hands of generals, administrators, governors, and local provincial lords; the Caliphs had lost all effective political power". These governments were still officially Islamic and committed to the religion, but religious authorities had developed their own hierarchies and bases of power separate from the political institutions governing them:

In the same period, religious communities developed independently of the states or empires that ruled them. The ulama regulated local communal and religious life by serving as judges, administrators, teachers, and religious advisers to Muslims. The religious elites were organized according to religious affiliation into Sunni schools of law, Shi'ite sects, or Sufi tariqas. [...] In the wide range of matters arising from the Shari'a - the Muslim law - the 'ulama' of the schools formed a local administrative and social elite whose authority was based upon religion.

Lapidus argues that the religious and political aspects of Muslim communal life came to be separated by Arab rebellions against the Caliphate, the emergence of religious activity independent of the actual authority of the Caliphs, and the emergence of the Hanbali school of law.

The Umayyad caliphate was seen as a secular state by many Muslims at the time, some of whom disapproved of the lack of integration of politics and religion. This perception was offset by a steady stream of wars that aimed to expand Muslim rule past the caliphate's borders.

In early Islamic philosophy, Averroes presented an argument in The Decisive Treatise providing a justification for the emancipation of science and philosophy from official Ash'ari theology. Because of this, some consider Averroism a precursor to modern secularism. Others argue that this reflects an incorrect view of his philosophy, stripped of its inherent Islamic dimensions by European philosophers.

Modern history

Many of the early supporters of Secularist principles in Middle Eastern countries were Baathist and non-Muslim Arabs, seeking a solution to a multi-confessional population and an ongoing drive to modernism.

Many Islamic modernist thinkers argued against the inseparability of religious and political authorities in the Islamic world, and described the system of separation between religion and state within their ideal Islamic world.

Muhammad ʿAbduh, a prominent Muslim modernist thinker, claimed in his book "Al-Idtihad fi Al-Nasraniyya wa Al-Islam" that no one had exclusive religious authority in the Islamic world. He argued that the Caliph did not represent religious authority, because he was not infallible nor was the Caliph the person whom the revelation was given to; therefore, according to Abduh, the Caliph and other Muslims are equal. ʿAbduh argued that the Caliph should have the respect of the umma but not rule it; the unity of the umma is a moral unity which does not prevent its division into national states.

Abdel Rahman Al-Kawakibi, in his book "Taba'i' Al-Istibdad (The Characteristics of Tyranny)", discussed the relationship between religion and despotism, arguing that "while most religions tried to enslave the people to the holders of religious office who exploited them, the original Islam was built on foundations of political freedom standing between democracy and aristocracy." Al-Kawakibi suggested that people can achieve a non-religious national unity, saying:"Let us take care of our lives in this world and let the religions rule in the next world." Moreover, in his second book "Umm Al-Qura (The Mother of Villages)" his most explicit statement with regard to the question of religion and state appeared in an appendix to the book, where he presented a dialogue between the Muslim scholar from India and an amir. The amir expressed his opinion that "religion is one thing and the government is another ... The administration of religion and the administration of the government were never united in Islam." 

Rashid Rida's thoughts about the separation of religion and state had some similarities with ʿAbduh and Al-Kawakibi. According to the scholar, Eliezer Tauber:

He was of the opinion that according to Islam 'the rule over the nation is in its own hands ... and its government is a sort of a republic. The caliph has no superiority in law over the lowest of the congregation; he only executes the religious law and the will of the nation.' And he added: 'For the Muslims, the caliph is not infallible (ma'sum) and not the source of revelation.' And therefore, 'the nation has the right to depose the imam-caliph, if it finds a reason for doing so'.

What is unique in Rida's thought is that he provided details of his ideas about the future Arab empire in a document, which he called the "General Organic Law of the Arab Empire". Rida argued that the general administrative policy of the future empire would be managed by a president, a council of deputies to be elected from the entire empire, and a council of ministers to be chosen by the president from among the deputies. There, the caliph must recognize the 'General Organic Law' and abide by it. He would manage all the religious matters of the empire. Rida's ideal Islamic empire would be administered in practice by a president, while the caliph would administer only religious affairs and would be obliged to recognize the organic law of the empire and abide by it.

As seen above, these arguments about separability of religious and political authorities in the Islamic world were greatly connected with the presence of the Caliphate. Therefore, the abolishment of the Caliphate by Turkish government in 1924 had considerable influence on such arguments among Muslim intellectuals. 

The most controversial work is that of Ali Abd al-Raziq, an Islamic Scholar and Shari’a judge who caused a sensation with his work "Islam and the Foundations of Governance (Al-Islam Wa Usul Al-Hukm)" in 1925. He argued that there were no clear evidence in the Quran and the hadith, which justify a common assumption: to accept the authority of the caliph is an obligation. Furthermore, he claimed that it was not even necessary that the ummah should be politically united and religion has nothing to do with one form of government rather than another. He argued that there is nothing in Islam which forbids Muslims to destroy their old political system and build a new one on the basis or the newest conceptions of the human spirit and the experience of nations. This publication caused a fierce debate especially as he recommended that religion can be separated from government and politics. He was later removed from his position. Rosenthall commented on him saying

"we meet for the first time a consistent, unequivocal theoretical assertion of the purely and exclusively religious character of Islam".

Taha Hussein, an Egyptian writer, was also an advocate for the separation of religion and politics from a viewpoint of Egyptian nationalism. Hussein believed that Egypt always had been part of Western civilization and that Egypt had its renaissance in the nineteenth century and had re-Europeanized itself. For him, the distinguishing mark of the modern world is that it has brought about a virtual separation of religion and civilization, each in its own sphere. It is therefore quite possible to take the bases of civilization from Europe without its religion, Christianity. Moreover, he believed that it is easier for Muslims than for Christian, since Islam has no priesthood, and so there has grown up no vested interest in the control of religion over society.

Secular feminism

Azza Karam (1998:13) describes secular feminists as follows: "Secular feminists firmly believe in grounding their discourse outside the realm of any religion, whether Muslim or Christian, and placing it, instead within the international human rights discourse. They do not ‘waste their time’ attempting to harmonize religious discourses with the concept and declarations pertinent to human rights. To them religion is respected as a private matter for each individual, but it is totally rejected as a basis from which to formulate any agenda on women’s emancipation. By so doing, they avoid being caught up in interminable debates on the position of women with religion." Generally, secular feminist activists call for total equality between the sexes, attempt to ground their ideas on women’s rights outside religious frameworks, perceive Islamism as an obstacle to their equality and a linkage to patriarchal values. They argue that secularism was important for protecting civil rights.

Secular states with majority Muslim populations

• Albania
• Azerbaijan
• Bosnia-Herzegovina
• Burkina Faso
• Chad
• Côte d'Ivoire
• Guinea
• Guinea-Bissau
• Indonesia (except Aceh)
• Kazakhstan
• Kosovo
• Kyrgyzstan
• Mali
• Niger
• Northern Cyprus
• Senegal
• Sierra Leone
• Tajikistan
• Turkey
• Turkmenistan
• Uzbekistan
• West Bank

Secularist movements by state

Turkey

Secularism in Turkey was both dramatic and far reaching as it filled the vacuum of the fall of the Ottoman Empire after World War I. With the country getting down Mustafa Kemal Atatürk led a political and cultural revolution. "Official Turkish modernity took shape basically through a negation of the Islamic Ottoman system and the adoption of a west-oriented mode of modernization."

• The Caliphate was abolished.
• Religious lodges and Sufi orders were banned.
• A secular civil code based on Swiss civil code was adopted to replace the previous codes based on Islamic law (shari’a) outlawing all forms of polygamy, annulled religious marriages, granted equal rights to men and women, in matters of inheritance, marriage and divorce.
• The religious court system and institutions of religious education were abolished.
• The use of religion for political purposes was banned.
• A separate institution was created that dealt with the religious matters of the people.
• The alphabet was changed from Arabic to Latin.
• A portion of religious activity was moved to the Turkish language, including the Adhan (call to prayer) which lasted until 1950. This was done by the second president of the republic of Turkey.

Throughout the 20th century secularism was continuously challenged by Islamists. At the end of the 20th century and beginning of the 21st century, political Islamists and Islamic democrats such as the Welfare Party and Justice and Development Party (AKP) gained in influence, with the AKP in the 2002 elections acquiring government and holding on to it ever since with increasingly authoritarian methods.

Lebanon

Lebanon is a parliamentary democracy within the overall framework of Confessionalism, a form of consociationalism in which the highest offices are proportionately reserved for representatives from certain religious communities. 

A growing number of Lebanese, however, have organized against the confessionalist system, advocating for an installation of laïcité in the national government. The most recent expression of this secularist advocacy was the Laïque Pride march held in Beirut on April 26, 2010, as a response to Hizb ut-Tahrir's growing appeal in Beirut and its call to re-establish the Islamic caliphate.

Tunisia

Under the leadership of Habib Bourguiba (1956–1987), Tunisia’s post independence government pursued a program of secularization.

Bourguiba modified laws regarding habous (religious endowments), secularized education and unified the legal system so that all Tunisians, regardless of religion, were subject to the state courts. He restricted the influence of the religious University of Ez-Zitouna and replaced it with a faculty of theology integrated into the University of Tunis, banned the headscarf for women, made members of the religious hierarchy state employees and ordered that the expenses for the upkeep of mosques and the salaries of preachers to be regulated.

Moreover, his best known legal innovations was the ‘Code du Statut Personel’ (CSP) the laws governs issues related to the family: marriage, guardianship of children, inheritance and most importantly the abolishing of polygamy and making divorce subject to judicial review.

Bourguiba clearly wanted to undercut the religious establishment’s ability to prevent his secularization program, and although he was careful to locate these changes within the framework of a modernist reading of Islam and presented them as the product of ijtihad (independent interpretation) and not a break with Islam, he became well known for his secularism. John Esposito says that "For Bourguiba, Islam represented the past; the west was Tunisia's only hope for a modern future, but he was mistaken, Islam is modernization"

Following increasing economic problems, Islamist movements came about in 1970 with the revival of religious teaching in Ez-Zitouna University and the influence which came from Arab religious leaders like Syrian and Egyptian Muslim Brotherhoods. There is also influence by Hizb ut-Tahrir, whose members issue a magazine in Tunis named Azeytouna. In the aftermath, the struggle between Bourguiba and Islamists became uncontrolled and in order to repress the opposition the Islamist leaderships were exiled, arrested and interrogated.

Ennahda Movement, also known as Renaissance Party or simply Ennahda, is a moderate Islamist political party in Tunisia. On 1 March 2011, after the secularist dictatorship of Zine El Abidine Ben Ali collapsed in the wake of the 2011 Tunisian revolution, Tunisia's interim government granted the group permission to form a political party. Since then it has become the biggest and most well-organized party in Tunisia, so far outdistancing its more secular competitors. In the Tunisian Constituent Assembly election, 2011, the first honest election in the country's history with a turn out of 51.1% of all eligible voters, the party won 37.04% of the popular vote and 89 (41%) of the 217 assembly seats, far more than any other party.

Egypt

Secularism in Egypt has had a very important role to play in both the history of Egypt and that of the Middle East. Egypt’s first experience of secularism started with the British Occupation (1882–1952), the atmosphere which allowed propagation of western ideas. In this environment, pro-secularist intellectuals like Ya'qub Sarruf, Faris Nimr, Nicola Haddad who sought political asylum from Ottoman Rule were able to publish their work. This debate had then become a burning issue with the work of Egyptian Shaykh Ali abd al-Raziq (1888–1966), "The most momentous document in the crucial intellectual and religious debate of modern Islamic history"

By 1919 Egypt had its first political secular entity called the Hizb 'Almani (Secular Party) this name was later changed to the Wafd party. It combined secular policies with a nationalist agenda and had the majority support in the following years against both the rule of the king and the British influence. The Wafd party supported the allies during World War II and then proceeded to win the 1952 parliamentary elections, following these elections the prime minister was overthrown by the King leading to riots. These riots precipitated a military coup after which all political parties were banned including the Wafd and the Muslim Brotherhood.

The government of Gamel Abdel Nasser was secularist-nationalist in nature which at the time gathers a great deal of support both in Egypt and other Arab states. Key elements of Nasserism:

• Secularist-Nationalist dictatorship: No religious or other political movements allowed to impact government.
• Modernization, Industrialization and Nationalization; Socialist economy
• Concentration on Arab values, identity and nationalism rather than Muslim values, identity and nationalism .

Secular legacy of Nasser's dictatorship influenced dictatorial periods of Anwar Sadat and Hosni Mubarak and secularists ruled Egypt until 2011 Egyptian revolution. Nevertheless, the Egyptian Muslim Brotherhood has become one of the most influential movements in the Islamic world, particularly in the Arab world. For many years it was described as "semi-legal" and was the only opposition group in Egypt able to field candidates during elections. In the Egyptian parliamentary election, 2011–2012, the political parties identified as "Islamist" (the Brotherhood's Freedom and Justice Party, Salafi Al-Nour Party and liberal Islamist Al-Wasat Party) won 75% of the total seats. Mohamed Morsi, an Islamist democrat of Muslim Brotherhood was the first democratically elected president of Egypt. Nowadays, most Egyptian proponents of secularism emphasize the link between secularism and ‘national unity’ between Coptic Christians and Muslims.

Syria

The process of secularization in Syria began under the French mandate in the 1920s and went on continuously under different governments since the independence. Syria has been governed by the Arab nationalist Ba'ath Party since 1963. The Ba'ath government combined Arab socialism with secular ideology and an authoritarian political system. The constitution guarantees religious freedom for every recognized religious communities, including many Christian denominations. All schools are government-run and non-sectarian, although there is mandatory religious instruction, provided in Islam and/or Christianity. Political forms of Islam are not tolerated by the government. The Syrian legal system is primarily based on civil law, and was heavily influenced by the period of French rule. It is also drawn in part from Egyptian law of Abdel Nasser, quite from the Ottoman Millet system and very little from Sharia. Syria has separate secular and religious courts. Civil and criminal cases are heard in secular courts, while the Sharia courts handle personal, family, and religious matters in cases between Muslims or between Muslims and non-Muslims. Non-Muslim communities have their own religious courts using their own religious law.

Iran

Following the military coup of 21 February 1921, Reza Khan had established himself as the dominant political personality in the country. Fearing that their influence might be diminished, the clergy of Iran proposed their support and persuaded him to assume the role of the Shah.

1925–1941: Reza Shah began to make some dramatic changes to Iranian society with the specific intention of westernization and removing religion from public sphere. He changed religious schools to secular schools, built Iran’s first secular university and banned the hijab in public. Nevertheless, the regime became totally undemocratic and authoritarian with the removal of Majles power (the first parliament in 1906) and the clampdown on free speech.

1951–1953: During the early 1950s, Prime Minister Mohammad Mosaddegh was again forming a secular government with a socialist agenda with the specific aim of reducing the power held by the clergy. However his plan to nationalize the colonial oil interests held by the Anglo-Iranian Oil Company, (later British Petroleum), attracted the ire of the United Kingdom. In response, the United Kingdom with the help of the CIA, supported a coup which removed Mossadeq from power and reinstated Mohammad Reza Shah.

1962–1963: Using the mandate of westernization, Mohammad Reza Shah introduced White Revolution, aiming to transform Iran into a Westernized secular capitalist country.

1963–1973: Opposition rallied united behind Ayatollah Ruhollah Khomeini and by the end of the 1970s the Shah was overthrown in an Islamic Revolution (1979).

Pakistan

Early in the history of the state of Pakistan (12 March 1949), a parliamentary resolution (the Objectives Resolution) was adopted, just a year after the death of Muhammad Ali Jinnah, the founder of Pakistan, in accordance with the vision of other founding fathers of Pakistan (Muhammad Iqbal, Liaquat Ali Khan). proclaiming:

Sovereignty belongs to Allah alone but He has delegated it to the State of Pakistan through its people for being exercised within the limits prescribed by Him as a sacred trust.

• The State shall exercise its powers and authority through the elected representatives of the people.
• The principles of democracy, freedom, equality, tolerance and social justice, as enunciated by Islam, shall be fully observed.
• Muslims shall be enabled to order their lives in the individual and collective spheres in accordance with the teachings of Islam as set out in the Quran and Sunnah.
• Provision shall be made for the religious minorities to freely profess and practice their religions and develop their cultures.

According to Pakistani secularists, this resolution differed from the Muhammad Ali Jinnah's 11th August Speech that he made in the Constitutive Assembly, but however, this resolution was passed by the rest of members in the assembly after Muhammad Ali Jinnah's death in 1948. This resolution later became key source of inspiration for writers of Constitution of Pakistan and is included in constitution as preamble. However, Pakistan is an Islamic republic, with Islam as the state religion; it has aspects of secularism inherited from its colonial past. Islamists and Islamic democratic parties in Pakistan are relatively less influential than democratic Islamists of other Muslim democracies however they do enjoy considerable street power.

The Council of Islamic Ideology is a body that is supposed to advise the Parliament of Pakistan on bringing laws and legislation in alignment with the principles of the Quran and Sunnah, though it has no enforcement powers. The Federal Shariat Court can strike down any law deemed un-Islamic, though its decisions can be overturned by the Supreme Court of Pakistan.

Opposition and critique

Secularism and religion

Islamists believe that Islam fuses religion and politics, with normative political values determined by the divine texts. It is argued that this has historically been the case and the secularist/modernist efforts at secularizing politics are little more than jahiliyyah (ignorance), kafir (unbelief/infidelity), irtidad (apostasy) and atheism. "Those who participated in secular politics were raising the flag of revolt against Allah and his messenger."

Saudi scholars denounce secularism as strictly prohibited in Islamic tradition. The Saudi Arabian Directorate of Ifta', Preaching and Guidance, has issued a directive decreeing that whoever believes that there is a guidance (huda) more perfect than that of the Prophet, or that someone else's rule is better than his is a kafir.

It lists a number of specific tenets which would be regarded as a serious departure from the precepts of Islam, punishable according to Islamic law. For example:

• The belief that human made laws and constitutions are superior to the Shari'a.
• The opinion that Islam is limited to one's relation with God, and has nothing to do with the daily affairs of life.
• To disapprove of the application of the hudud (legal punishments decreed by God) that they are incompatible in the modern age.
• And whoever allows what God has prohibited is a kafir.

In the view of Tariq al-Bishri, "secularism and Islam cannot agree except by means of talfiq [combining the doctrines of more than one school, i.e., falsification], or by each turning away from its true meaning."

Secularism and authoritarianism

A number of scholars believe that secular governments in Muslim countries have become more repressive and authoritarian to combat the spread of Islamism, but this increased repression may have made many Muslim societies more opposed to secularism and increased the popularity of Islamism the Middle East.

Authoritarianism has left in many countries the mosque as the only place to voice political opposition. Scholars like Vali Nasr argue that the secular elites in the Muslim world were imposed by colonial powers to maintain hegemony.

Secularism is also associated with military regimes, such as those in Turkey and Algeria. The Islamic Salvation Front (FIS) succeeded in December 1991 elections in Algeria and the Welfare Party succeeded in the Turkish 1995 elections. However, both of these parties were eliminated through military coups in order to protect secularism. While Welfare Party government in Turkey was forced to resign from the office by Turkish military in February 1997 with a military intervention which is called as "post modern coup", FIS in Algeria lived an austere military coup which carried the country in to a civil war in 1992. Military forces in those countries could use their power in undemocratic ways in order to ‘protect secularism’.

In some countries, the fear of Islamist takeover via democratic processes has led to authoritarian measures against Islamist political parties. "The Syrian regime was able to capitalize on the fear of Islamist coming to power to justify the massive clampdown on the Syrian Muslim Brotherhood." When American diplomats asked Hosni Mubarak to give more rights to the press and stop arresting the intellectuals, Mubarak rejected it and said, "If I do what you ask, the fundamentalists will take over the government in Egypt. Do you want that?" Or when President Bill Clinton asked Yasser Arafat to establish democracy in Palestine in 2001, Yasser Arafat also replied similarly. "He said that in a democratic system Islamist Hamas will surely take control of the government in Palestine". Most secularist autocrats in the Middle East drew upon the risk of Islamism in order to justify their autocratic rule of government in the international arena.