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Wednesday, July 5, 2023

Hydrogen line

From Wikipedia, the free encyclopedia

A hydrogen atom with proton and electron spins aligned (top) undergoes a flip of the electron spin, resulting in emission of a photon with a 21 cm wavelength (bottom)

The hydrogen line, 21 centimeter line, or H I line is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms. It is produced by a spin-flip transition, which means the direction of the electron's spin is reversed relative to the spin of the proton. This is a quantum state change between the two hyperfine levels of the hydrogen 1 s ground state. The electromagnetic radiation producing this line has a frequency of 1420.405751768(2) MHz (1.42 GHz), which is equivalent to a wavelength of 21.106114054160(30) cm in a vacuum. According to the Planck–Einstein relation $E = hν$ , the photon emitted by this transition has an energy of 5.8743261841116(81) μeV [9.411708152678(13)×10⁻²⁵ J]. The constant of proportionality, $h$ , is known as the Planck constant.

The hydrogen line frequency lies in the L band, which is located in the lower end of the microwave region of the electromagnetic spectrum. It is frequently observed in radio astronomy because those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light. The existence of this line was predicted by Dutch astronomer H. van de Hulst in 1944, then directly observed by E. M. Purcell and his student H. E. Ewen in 1951. Observations of the hydrogen line have been used to reveal the spiral shape of the Milky Way, to calculate the mass and dynamics of individual galaxies, and to test for changes to the fine-structure constant over time. It is of particular importance to cosmology because it can be used to study the early Universe. Due to its fundamental properties, this line is of interest in the search for extraterrestrial intelligence. This line is the theoretical basis of the hydrogen maser.

Cause

The ground state of neutral hydrogen consists of an electron bound to a proton. Both the electron and the proton have intrinsic magnetic dipole moments ascribed to their spin, whose interaction results in a slight increase in energy when the spins are parallel, and a decrease when antiparallel. The fact that only parallel and antiparallel states are allowed is a result of the quantum mechanical discretization of the total angular momentum of the system. When the spins are parallel, the magnetic dipole moments are antiparallel (because the electron and proton have opposite charge), thus one would expect this configuration to actually have lower energy just as two magnets will align so that the north pole of one is closest to the south pole of the other. This logic fails here because the wave functions of the electron and the proton overlap; that is, the electron is not spatially displaced from the proton, but encompasses it. The magnetic dipole moments are therefore best thought of as tiny current loops. As parallel currents attract, the parallel magnetic dipole moments (i.e., antiparallel spins) have lower energy.

The spin-flip transition between these aligned states has an energy difference of 5.87433 μeV. When applied to the Planck relation, this gives:

λ = \frac{1}{ν} \cdot c = \frac{h}{E} \cdot c \approx \frac{4.1357 \cdot 10^{- 15} e V \cdot s}{5.874 33 \cdot 10^{- 6} e V} \cdot 2.9979 \cdot 10^{8} m \cdot s^{- 1} \approx 0.211 06 m = 21.106 c m

where $λ$ is the wavelength of an emitted photon, $ν$ is its frequency, $E$ is the photon energy, $h$ is the Planck constant, and $c$ is the speed of light. In a laboratory setting, the hydrogen line parameters have been more precisely measured as:

λ = 21.106114054160(30) cm

ν = 1420405751.768(2) Hz

in a vacuum.

This transition is highly forbidden with an extremely small transition rate of 2.9×10⁻¹⁵ s⁻¹, and a mean lifetime of the excited state of around 11 million years. Collisions of neutral hydrogen atoms with electrons or other atoms can help promote the emission of 21-cm photons. A spontaneous occurrence of the transition is unlikely to be seen in a laboratory on Earth, but it can be artificially induced through stimulated emission using a hydrogen maser. It is commonly observed in astronomical settings such as hydrogen clouds in our galaxy and others. Because of the uncertainty principle, its long lifetime gives the line an extremely small natural width, so most broadening is due to Doppler shifts caused by bulk motion or nonzero temperature of the emitting regions.

Discovery

Horn antenna used by Ewen and Purcell for the first detection of hydrogen line emission from the Milky Way

During the 1930s, it was noticed that there was a radio "hiss" that varied on a daily cycle and appeared to be extraterrestrial in origin. After initial suggestions that this was due to the Sun, it was observed that the radio waves seemed to propagate from the centre of the Galaxy. These discoveries were published in 1940 and were noted by Jan Oort who knew that significant advances could be made in astronomy if there were emission lines in the radio part of the spectrum. He referred this to Hendrik van de Hulst who, in 1944, predicted that neutral hydrogen could produce radiation at a frequency of 1420.4058 MHz due to two closely spaced energy levels in the ground state of the hydrogen atom.

The 21 cm line (1420.4 MHz) was first detected in 1951 by Ewen and Purcell at Harvard University, and published after their data was corroborated by Dutch astronomers Muller and Oort, and by Christiansen and Hindman in Australia. After 1952 the first maps of the neutral hydrogen in the Galaxy were made, and revealed for the first time the spiral structure of the Milky Way.

Uses

In radio astronomy

The 21 cm spectral line appears within the radio spectrum (in the L band of the UHF band of the microwave window to be exact). Electromagnetic energy in this range can easily pass through the Earth's atmosphere and be observed from the Earth with little interference. The hydrogen line can readily penetrate clouds of interstellar cosmic dust that are opaque to visible light. Assuming that the hydrogen atoms are uniformly distributed throughout the galaxy, each line of sight through the galaxy will reveal a hydrogen line. The only difference between each of these lines is the Doppler shift that each of these lines has. Hence, by assuming circular motion, one can calculate the relative speed of each arm of our galaxy. The rotation curve of our galaxy has been calculated using the 21 cm hydrogen line. It is then possible to use the plot of the rotation curve and the velocity to determine the distance to a certain point within the galaxy. However, a limitation of this method is that departures from circular motion are observed at various scales.

Hydrogen line observations have been used indirectly to calculate the mass of galaxies, to put limits on any changes over time of the fine-structure constant, and to study the dynamics of individual galaxies. The magnetic field strength of interstellar space can be measured by observing the Zeeman effect on the 21-cm line; a task that was first accomplished by G. L. Verschuur in 1968. In theory, it may be possible to search for antihydrogen atoms by measuring the polarization of the 21-cm line in an external magnetic field.

In cosmology

The line is of great interest in Big Bang cosmology because it is the only known way to probe the cosmological "dark ages" from recombination (when stable hydrogen atoms first formed) to reionization. Including the redshift, this line will be observed at frequencies from 200 MHz to about 15 MHz on Earth. It potentially has two applications. First, by mapping the intensity of redshifted 21 centimeter radiation it can, in principle, provide a very precise picture of the matter power spectrum in the period after recombination. Second, it can provide a picture of how the universe was re‑ionized, as neutral hydrogen which has been ionized by radiation from stars or quasars will appear as holes in the 21 cm background.

However, 21 cm observations are very difficult to make. Ground-based experiments to observe the faint signal are plagued by interference from television transmitters and the ionosphere, so they must be made from very secluded sites with care taken to eliminate interference. Space based experiments, even on the far side of the Moon (where they would be sheltered from interference from terrestrial radio signals), have been proposed to compensate for this. Little is known about other foreground effects, such as synchrotron emission and free–free emission on the galaxy. Despite these problems, 21 cm observations, along with space-based gravitational wave observations, are generally viewed as the next great frontier in observational cosmology, after the cosmic microwave background polarization.

Relevance to the search for non-human intelligent life

The hyperfine transition of hydrogen, as depicted on the Pioneer and Voyager spacecraft.

The Pioneer plaque, attached to the Pioneer 10 and Pioneer 11 spacecraft, portrays the hyperfine transition of neutral hydrogen and used the wavelength as a standard scale of measurement. For example, the height of the woman in the image is displayed as eight times 21 cm, or 168 cm. Similarly the frequency of the hydrogen spin-flip transition was used for a unit of time in a map to Earth included on the Pioneer plaques and also the Voyager 1 and Voyager 2 probes. On this map, the position of the Sun is portrayed relative to 14 pulsars whose rotation period circa 1977 is given as a multiple of the frequency of the hydrogen spin-flip transition. It is theorized by the plaque's creators that an advanced civilization would then be able to use the locations of these pulsars to locate the Solar System at the time the spacecraft were launched.

The 21 cm hydrogen line is considered a favorable frequency by the SETI program in their search for signals from potential extraterrestrial civilizations. In 1959, Italian physicist Giuseppe Cocconi and American physicist Philip Morrison published "Searching for interstellar communications", a paper proposing the 21 cm hydrogen line and the potential of microwaves in the search for interstellar communications. According to George Basalla, the paper by Cocconi and Morrison "provided a reasonable theoretical basis" for the then-nascent SETI program. Similarly, Pyotr Makovetsky proposed SETI use a frequency which is equal to either

π

× 1420.40575177 MHz ≈ 4.46233627 GHz

π

× 1420.40575177 MHz ≈ 8.92467255 GHz

Since $π$ is an irrational number, such a frequency could not possibly be produced in a natural way as a harmonic, and would clearly signify its artificial origin. Such a signal would not be overwhelmed by the H I line itself, or by any of its harmonics.

Period 1 element

https://en.wikipedia.org/wiki/Period_1_element

A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate periodic (recurring) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that analog elements fall into the same vertical columns. The first period contains fewer elements than any other row in the table, with only two: hydrogen and helium. This situation can be explained by modern theories of atomic structure. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 1s orbital. Period 1 elements obey the duet rule in that they need two electrons to complete their valence shell.

Hydrogen and helium are the oldest and the most abundant elements in the universe.

Periodic trends

All other periods in the periodic table contain at least eight elements, and it is often helpful to consider periodic trends across the period. However, period 1 contains only two elements, so this concept does not apply here.

In terms of vertical trends down groups, helium can be seen as a typical noble gas at the head of the IUPAC group 18, but as discussed below, hydrogen's chemistry is unique and it is not easily assigned to any group.

Position of period 1 elements in the periodic table

The first electron shell, $n = 1$ , consists of only one orbital, and the maximum number of valence electrons that a period 1 element can accommodate is two, both in the 1s orbital. The valence shell lacks "p" or any other kind of orbitals due to the general $l < n$ constraint on the quantum numbers. Therefore, period 1 has exactly two elements. Although both hydrogen and helium are in the s-block, neither of them behaves similarly to other s-block elements. Their behaviour is so different from the other s-block elements that there is considerable disagreement over where these two elements should be placed in the periodic table.

Simply following electron configurations, hydrogen (electronic configuration 1s¹) and helium (1s²) should be placed in groups 1 and 2, above lithium (1s²2s¹) and beryllium (1s²2s²). While such a placement is common for hydrogen, it is rarely used for helium outside of the context of illustrating the electron configurations. Usually, hydrogen is placed in group 1, and helium in group 18: this is the placement found on the IUPAC periodic table. Some variation can be found on both these matters.

Like the group 1 metals, hydrogen has one electron in its outermost shell and typically loses its only electron in chemical reactions. It has some metal-like chemical properties, being able to displace some metals from their salts. But hydrogen forms a diatomic nonmetallic gas at standard conditions, unlike the alkali metals which are reactive solid metals. This and hydrogen's formation of hydrides, in which it gains an electron, brings it close to the properties of the halogens which do the same (though it is rarer for hydrogen to form H⁻ than H⁺). Moreover, the lightest two halogens (fluorine and chlorine) are gaseous like hydrogen at standard conditions. Some properties of hydrogen are not a good fit for either group: hydrogen is neither highly oxidising nor highly reducing and is not reactive with water. Hydrogen thus has properties corresponding to both those of the alkali metals and the halogens, but matches neither group perfectly, and is thus difficult to place by its chemistry. Therefore, while the electronic placement of hydrogen in group 1 predominates, some rarer arrangements show either hydrogen in group 17, duplicate hydrogen in both groups 1 and 17, or float it separately from all groups. The possibility of "floating" hydrogen has nonetheless been criticised by Eric Scerri, who points out that removing it from all groups suggests that it is being excluded from the periodic law, when all elements should be subject to that law. A few authors have advocated more unusual placements for hydrogen, such as group 13 or group 14, on the grounds of trends in ionisation energy, electron affinity, and electronegativity.

Helium is an unreactive noble gas at standard conditions, and has a full outer shell: these properties are like the noble gases in group 18, but not at all like the reactive alkaline earth metals of group 2. Therefore, helium is nearly universally placed in group 18 which its properties best match. However, helium only has two outer electrons in its outer shell, whereas the other noble gases have eight; and it is an s-block element, whereas all other noble gases are p-block elements. Also, solid helium crystallises in a hexagonal close-packed structure, which matches beryllium and magnesium in group 2, but not the other noble gases in group 18. In these ways helium better matches the alkaline earth metals.Therefore, tables with both hydrogen and helium floating outside all groups may rarely be encountered.

A few chemists, such as Henry Bent, have advocated that the electronic placement in group 2 be adopted for helium. This assignment is also found in Charles Janet's left-step table. Arguments for this often rest on the first-row anomaly trend (s >> p > d > f), which states that the first element of each group often behaves quite differently from the succeeding ones: the difference is largest in the s-block (H and He), is moderate for the p-block (B to Ne), and is less pronounced for the d- and f-blocks. Thus helium as the first s² element before the alkaline earth metals stands out as anomalous in a way that helium as the first noble gas does not. The normalized ionization potentials and electron affinities show better trends with helium in group 2 than in group 18; helium is expected to be slightly more reactive than neon (which breaks the general trend of reactivity in the noble gases, where the heavier ones are more reactive); and predicted helium compounds often lack neon analogues even theoretically, but sometimes have beryllium analogues.

Elements

Chemical element			Block	Electron configuration
1	H	Hydrogen	s-block	1s¹
2	He	Helium	s-block	1s²

Hydrogen

Hydrogen discharge tube

Deuterium discharge tube

Hydrogen (H) is the chemical element with atomic number 1. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H₂. With an atomic mass of 1.00794 amu, hydrogen is the lightest element.

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally divided between fossil fuel upgrading, such as hydrocracking, and ammonia production, mostly for the fertilizer market. Hydrogen may be produced from water using the process of electrolysis, but this process is significantly more expensive commercially than hydrogen production from natural gas.

The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons. In ionic compounds, it can take on either a positive charge, becoming a cation composed of a bare proton, or a negative charge, becoming an anion known as a hydride. Hydrogen can form compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and spectrum of the hydrogen atom has played a key role in the development of quantum mechanics.

The interactions of hydrogen with various metals are very important in metallurgy, as many metals can suffer hydrogen embrittlement, and in developing safe ways to store it for use as a fuel. Hydrogen is highly soluble in many compounds composed of rare earth metals and transition metals and can be dissolved in both crystalline and amorphous metals. Hydrogen solubility in metals is influenced by local distortions or impurities in the metal crystal lattice.

Helium

Helium discharge tube

Helium (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas series in the periodic table and whose atomic number is 2. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.

Helium was discovered in 1868 by French astronomer Pierre Janssen, who first detected the substance as an unknown yellow spectral line signature in light from a solar eclipse. In 1903, large reserves of helium were found in the natural gas fields of the United States, which is by far the largest supplier of the gas. The substance is used in cryogenics, in deep-sea breathing systems, to cool superconducting magnets, in helium dating, for inflating balloons, for providing lift in airships, and as a protective gas for industrial uses such as arc welding and growing silicon wafers. Inhaling a small volume of the gas temporarily changes the timbre and quality of the human voice. The behavior of liquid helium-4's two fluid phases, helium I and helium II, is important to researchers studying quantum mechanics and the phenomenon of superfluidity in particular, and to those looking at the effects that temperatures near absolute zero have on matter, such as with superconductivity.

Helium is the second lightest element and is the second most abundant in the observable universe. Most helium was formed during the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen in stars. On Earth, helium is relatively rare and is created by the natural decay of some radioactive elements because the alpha particles that are emitted consist of helium nuclei. This radiogenic helium is trapped with natural gas in concentrations of up to seven percent by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation.

Expulsions and exoduses of Jews

From Wikipedia, the free encyclopedia



https://en.wikipedia.org/wiki/Expulsions_and_exoduses_of_Jews

Timeline

The following is a list of Jewish expulsions and events that prompted significant streams of Jewish refugees.

Assyrian captivity

733/2 BCE: Tiglath-Pileser III, King of the Neo-Assyrian Empire, sacked the northern Kingdom of Israel and annexed the territory of the tribes of Reuben, Gad and Manasseh in Gilead. People from these tribes were taken captive and resettled in the region of the Khabur River, in Halah, Habor, Hara and Gozan (1 Chronicles 5:26). Tiglath-Pileser also captured the territory of Naphtali and the city of Janoah in Ephraim, and an Assyrian governor was placed over the region of Naphtali. According to 2 Kings 15:29, the population of Naphtali was deported to Assyria.

722 BCE: In 722 BCE, Samaria, the capital city of the northern Kingdom of Israel, was taken by Sargon II, who resettled the Israelites in Halah, Habor, Gozan and in the cities of Media (2 Kings 18:11–12). Sargon recorded the capture of that city thus: "Samaria I looked at, I captured; 27,280 men who dwelt in it I carried away" into Assyria. Some people of the northern tribes were spared, and it has been suggested that many also fled south to Jerusalem.

Babylonian Captivity

597 BCE: In 598 BCE, Nebuchadnezzar II of the Neo-Babylonian Empire besieged Jerusalem, then capital of the southern Kingdom of Judah. The city fell after a three-month siege, and the new king Jeconiah, who was either 8 or 18, his court and other prominent citizens (including the prophet Ezekiel) and craftsmen, were deported to Babylon. Jehoiakim's uncle Zedekiah was appointed king in his place.

587-586 BCE

When Zedekiah revolted against Babylonian rule, Nebuchadnezzar responded by invading Judah (2 Kings 25:1). In December 589 BCE, Nebuchadnezzar began another siege of Jerusalem.^[6] During the siege, many Jews fled to surrounding Moab, Ammon, Edom and other countries to seek refuge. The city eventually fell after a thirty-month siege, and the Babylonian general Nebuzaradan was sent to complete its destruction. The city was plundered, and Solomon's Temple was destroyed. Most of the members of the elite class were taken into captivity in Babylon. The city was razed. Only a few people were permitted to remain and tend to the land (Jeremiah 52:16).: In 537 BCE Cyrus the Great, the founding king of the Achaemenid Persian Empire, allowed the Jews to return to Judah and rebuild the Temple.

Fall of Jerusalem; Solomon's Temple is on fire

500-1 BCE

139 BCE: Expulsion from the city of Rome under the accusation of aggressive proselytizing among the Romans.

1-599 CE

19 CE: Expulsion from the city of Rome by Emperor Tiberius together with practitioners of the Egyptian religion.

38 CE: Jews were expelled from one of their quarters in the city of Alexandria, in Egypt, under the instigation of Aulus Avilius Flaccus.

41-53 CE: Claudius' expulsion of Jews from Rome.

73 CE: The Jewish defeat in the First Jewish–Roman War led to many Jews being taken prisoner and enslaved or becoming refugees.

119: Large Jewish communities of Cyprus, Cyrene and Alexandria obliterated after the Jewish defeat in Kitos War against Rome. This event caused a major demographic shift in the Levant and North Africa. According to Eusebius of Caesarea the outbreak of violence left Libya depopulated to such an extent that a few years later new colonies had to be established there by the emperor Hadrian just to maintain the viability of continued settlement.

415: Jews expelled from Alexandria under the leadership of Saint Cyril of Alexandria.

418: Jews expelled from Minorca or asked to convert.

Sixth to tenth centuries

612: Visigothic king Sisebut mandated that every Jew who would refuse for over a year to have himself or his children and servants baptized would be banished from the country and deprived of his possessions.

629: The entire Jewish population of Galilee massacred or expelled, following the Jewish rebellion against Byzantium.

7th century: Muhammad expelled two Jewish tribes: the Banu Qaynuqa and Banu Nadir from Medina. The Banu Qurayza tribe was slaughtered and the Jewish settlement of Khaybar was ransacked.

Eleventh to thirteenth centuries

1012

Jews expelled from Mainz.

Expulsions of Jews in Europe from 1100 to 1600

1095–mid-13th century: The waves of Crusades destroyed many Jewish communities in Europe (most notably in Rhineland) and in the Middle East (most notably in Jerusalem).

Mid-12th century: The invasion of Almohades brought to an end the Golden age of Jewish culture in Spain. Among other refugees was Maimonides, who fled to Morocco, then Egypt, then Eretz Israel.

1276: Jews expelled from Upper Bavaria.

12th–14th centuries: France. The practice of expelling the Jews accompanied by confiscation of their property, followed by temporary readmissions for ransom, was used to enrich the crown: expulsions from Paris by Philip Augustus in 1182, from France by Louis IX in 1254, by Philip IV in 1306, by Charles IV in 1322, by Charles V in 1359, by Charles VI in 1394.

13th century: The influential philosopher and logician Ramon Llull (1232–1315) called for expulsion of all Jews who would refuse conversion to Christianity. Some scholars regard Llull's as the first comprehensive articulation, in the Christian West, of an expulsionist policy regarding Jews.

1253: On July 23 (Menachem Av 25) the Jews of Vienne, France were expelled by order of Pope Innocent III

1288: Naples issues first expulsion of Jews in Southern Italy.

1290: King Edward I of England issues the Edict of Expulsion for all Jews from England. The policy was reversed after 365 years in 1655 by Oliver Cromwell.

1294: On June 24 (4th of Tamuz), the Jews of Berne, Switzerland were expelled "Several Jews were put to death there in consequence of a blood libel" but a deal involving the Jews paying money reverted the expulsion.

14th century

1360: Jews expelled from Hungary by Louis I of Hungary.^[27]

1392: Jews expelled from Bern, Switzerland. Although between 1408 and 1427 Jews were again residing in the city, the only Jews to appear in Bern subsequently were transients, chiefly physicians and cattle dealers.

15th century

1420-21: Duke Albert V orders the imprisonment and forcible conversion to Christianity of all Jews in Austria. Some convert and others leave the country. In 1421 Austrian authorities again arrest and expel Jews and Jews are banned from the capital Vienna.

1442: Jews again expelled from Upper Bavaria.

1478: Jews expelled from Passau.

1491: Jews of Ravenna expelled, synagogues destroyed.

1492: Ferdinand II and Isabella I issued the Alhambra decree, General Edict on the Expulsion of the Jews from Spain (approx. 200,000) and from Sicily (1493, approx. 37,000).

1495: Charles VIII of France occupies Kingdom of Naples, bringing new persecution against Jews, many of whom were refugees from Spain.^[24]

1496: Jews expelled from Portugal. Maximilian I, Holy Roman Emperor, issues a decree expelling all Jews from Styria and Wiener Neustadt.

1499: Jews expelled from Nuremberg.

16th century

1510: Jews expelled from Naples.
1510: Jews expelled from Brandenburg after a false accusation of host desecration in Berlin.

1519: Jews expelled from Regensburg.

1526: Jews expelled from Pressburg (Bratislava) in the wake of the defeat of the Kingdom of Hungary by the Ottoman Empire.

1551: All remaining Jews expelled from the duchy of Bavaria. Jewish settlement in Bavaria ceased until toward the end of the 17th century, when a small community was founded in Sulzbach by refugees from Vienna.

1569: Pope Pius V expels Jews from the papal states, except for Ancona and Rome.

1593: Pope Clement VIII expels Jews living in all the papal states, except Rome, Avignon and Ancona. Jews are invited to settle in Leghorn, the main port of Tuscany, where they are granted full religious liberty and civil rights, by the Medici family, who want to develop the region into a center of commerce.

1597: Nine hundred Jews were expelled from Milan.

17th century

1614: Fettmilch Uprising: Jews are expelled from Frankfurt, Holy Roman Empire, following the plundering of the Judengasse.

1654: The fall of the Dutch colony of Recife in Brazil to the Portuguese prompted the Jewish arrival in New Amsterdam, the first group of Jews to flee to North America.

1669-1670: Jews expelled from Vienna by Leopold I, Holy Roman Emperor and subsequently forbidden to settle in the Austrian Hereditary Lands. The former Jewish ghetto on the Unterer Werd was renamed Leopoldstadt in honour of the emperor and the expropriated houses and land given to Catholic citizens.

1679–1680: Jews all throughout Yemen expelled from their towns and villages and sent to a desert place, in what is known as the Mawza Exile.

1683: Jews expelled from Haiti and all of the other French colonies, due to the Code Noir decree issued by Louis XIV.

18th century

1701–1714: War of the Spanish Succession. After the war, Jews of Austrian origin were expelled from Bavaria, but some were able to acquire the right to reside in Munich.

1744–1790s: The reforms of Frederick II, Joseph II and Maria Theresa sent masses of impoverished German and Austrian Jews east.

1791: The tzarina of Russia Catherine the Great institutes the Pale of Settlement, restricting Jews to the western parts of the empire by means of deportation. By the late 19th century, over four million Jews would live in the Pale.

19th century

1862 Tennessee, Mississippi, Kentucky: Jews expelled by Ulysses S. Grant by General Order No. 11.

1880-1910s: Pogroms in the Russian Empire: around 2.5 million Jews emigrated from eastern Europe, mostly to the United States.

20th century

1917: Jews expelled from the area of Jaffa by Ottoman authorities during World War I.

1933–1957

First Batch of Refugee children arrive in England from Germany.

Buchenwald survivors arrive in Haifa.

The Nazi German persecution started with the Nazi boycott of Jewish businesses in 1933, reached a first climax during Kristallnacht in 1938 and culminated in the Holocaust of European Jewry. The British Mandate of Palestine prohibited Jewish emigration to Mandatory Palestine. The 1938 Evian Conference, the 1943 Bermuda Conference and other attempts failed to resolve the problem of Jewish refugees, a fact widely used in Nazi propaganda. A small number of German and Austrian Jewish refugees from Nazism emigrated to Britain, where attitudes were not necessarily positive. Many of the refugees fought for Britain in the Second World War. After WW-II, eastern European Holocaust survivors migrated to the allied-controlled part of Europe, as the Jewish society to which most of them belonged did not exist anymore. Often they were lone survivors consumed by the often futile search for other family and friends, and often unwelcome in the towns from which they came. They were known as displaced persons (also known as Sh'erit ha-Pletah) and placed in displaced persons camps, most of which were by 1951 closed. The last camp Föhrenwald was closed in 1957.

1943-1944: Jews are expelled, their citizenship is stripped from them and they are subjected to pogroms in some Italian cities, including Rome, Verona, Florence, Pisa and Alessandria.

1947–1972

Jewish refugees look out through the portholes of a ship while it is docked in the port city of Haifa.

Iraqi Jews displaced 1951.

The Exodus bringing in refugees.

In the course of the operation "Magic Carpet" (1949–1950), most of the community of Yemenite Jews (called Teimanim, about 49,000) immigrated to Israel.

The Jewish exodus from the Muslim world, in which the combined population of the Jewish communities of the Middle East and North Africa (excluding Israel) was reduced from about 900,000 in 1948 to under 8,000 today, and approximately 600,000 of them became citizens of Israel. The history of the exodus is politicized, given its proposed relevance to a final settlement to the Israeli–Palestinian peace negotiations. When presenting the history, those who view the Jewish exodus as equivalent to the 1948 Palestinian exodus, such as the Israeli government and NGOs such as JJAC and JIMENA, emphasize "push factors", such as cases of anti-Jewish violence and forced expulsions, and refer to those affected as "refugees". Those who argue that the exodus does not equate to the Palestinian exodus emphasize "pull factors", such as the actions of local Jewish Agency for Israel officials aiming to fulfil the One Million Plan, highlight good relations between the Jewish communities and their country's governments, emphasize the impact of other push factors such as the decolonization in the Maghreb and the Suez War and Lavon Affair in Egypt, and argue that many or all of those who left were not refugees.

Then UNHCR announced in February 1957 and in July 1967, that these Jews who had fled from Arab countries "may be considered prima facie within the mandate of this office," so according them in international law, as bona fide refugees.

1947: Egypt passed the Companies' Law. This law required that no less than 75% of employees of companies in Egypt must be Egyptian citizens. This law strongly affected Jews, as only about 20% of all Jews in Egypt were Egyptian citizens. The rest, although in many cases born in Egypt and living there for generations, did not hold Egyptian citizenship.

1948: State of Israel established. Antisemitism in Egypt strongly intensified. On May 15, 1948, emergency law was declared, and a royal decree forbade Egyptian citizens to leave the country without a special permit. This was applied to Jews. Hundreds of Jews were arrested and many had their property confiscated. In June through August 1948, bombs were planted in Jewish neighborhoods and Jewish businesses looted. About 250 Jews were killed or wounded by the bombs. Roughly 14,000 Jews left Egypt between 1948 and 1950.

1949: Jordan occupies and then annexes the West Bank – largely allotted by the 1947 UN Partition of Palestine to an Arab state, proposal rejected by the Arab leadership – and conducts large scale discrimination and persecution of all non-Muslim residents – Jewish, Christian (of many denominations), Druze, Circassian, etc. – and forces Arabisation of all public activity, including schools and public administration.

1951-1952: During Operation Ezra and Nehemiah, ~120,000 Jews Expelled under the De-Naturalization Act of Iraqi PM Tawfeeq Al-Suwaidi due to Jews having too much influence over the economy.

1954: Gamal Abdel Nasser seizes power in Egypt. Nasser immediately arrested many Jews who were tried on various charges, mainly for Zionist and communist activities. Jews were forced to donate large sums of money to the military. Strict supervision of Jewish enterprises was introduced; some were confiscated and others forcibly sold to the government.

1956: Suez Crisis. Roughly 3,000 Egyptian Jews were interned without charge in four detention camps. The government ordered thousands of Jews to leave the country within a few days, and they were not allowed to sell their property, nor to take any capital with them. The deportees were made to sign statements agreeing not to return to Egypt and transferring their property to the administration of the government. The International Red Cross helped about 8,000 stateless Jews to leave the country, taking most of them to Italy and Greece. Most of the Jews of Port Said (about 100) were smuggled to Israel by Israel agents. The system of deportation continued into 1957. Other Jews left voluntarily, after their livelihoods had been taken from them, until only 8,561 were registered in the 1957 census. The Jewish exodus continued until there were about 3,000 Jews left as of in 1967.

1962: Jews flee Algeria as result of OAS violence. The community feared that the proclamation of independence would precipitate a Muslim outburst. By the end of July 1962, 70,000 Jews had left for France and another 5,000 for Israel. It is estimated that some 80% of Algerian Jews settled in France.

1965: Situation of Jews in Algeria rapidly deteriorates. By 1969, fewer than 1,000 Jews remain. By the 1990s, the numbers had dwindled to approximately 70.

1967: Six-Day War. Hundreds of Egyptian Jews arrested, suffering beatings, torture, and abuse. Some were released following intervention by foreign states, especially by Spain, and were permitted to leave the country. Libyan Jews, who numbered approximately 7,000, were subjected to pogroms in which 18 were killed, prompting a mass exodus that left fewer than 100 Jews in Libya.

1968: 1968 Polish political crisis forced thousands of Jews to leave communist Poland.

1970: Less than 1,000 Jews still lived in Egypt in 1970. They were given permission to leave but without their possessions. As of 1971, only 400 Jews remained in Egypt. As of 2013, only a few dozen Jews remain in Egypt. As of 2019, there were five in Cairo. As of 2022 the total number of known Egyptian Jews permanently residing in Egypt is three.

1970s–1990s: State-sponsored persecution in the Soviet Union prompted hundreds of thousands of Soviet Jews, known as Refuseniks because they had been denied official permission to leave, to flee; most went to Israel or to the United States as refugees.
1972: Idi Amin, expels all Israelis from Uganda.
1985 and 1991: 10,000 Jews fled Ethiopia as part of Operation Moses and Operation Joshua and 14,000 Jews fled Ethiopia as part of Operation Solomon.

21st century

2003: Last Jew left Libya.
2010: Contact with last two Jews in Somalia was lost.
2021: Last Jews left Afghanistan.
2021: Members of Yemen's Jewish community have fled the country, leaving only six reported Jews left, though it is not clear whether they were expelled or left voluntarily as part of an exit agreement with the Houthi movement. One of the expelled family members said:
“History will remember us as the last of Yemeni Jews who were still clinging to their homeland until the last moment,” “We had rejected many temptations time and time again, and refused to leave our homeland, but today we are forced.”

On 28 March 2021, 13 Jews were forced by the Houthis to leave Yemen, The Jerusalem Post reported that the remaining Jewish population in Yemen consists of four elderly Jews in Yemen ending the continuous presence of a community that dated back to antiquity. According to one report there are six Jews left in Yemen: one woman; her brother; 3 others, and Levi Salem Marhabi (who has been imprisoned for helping smuggle a Torah scroll out of Yemen). In December 2021 the Jews of Yemen received Hanukkah kits. In March 2022 the United Nations reports there is just 1 Jew in Yemen (Levi Salem Marhabi).

2022: ... 7635384142 World Jewish Congress website "Jews lived in Algeria from the pre-Roman period to the early 1960s. There is no Jewish community left in Algeria today."(Accessed 18 March 2022)
2022: The number of living Jews in Iraq is 3 (2022).On May 27, 2022, Iraq passed a law making contact with Israel punishable by death.