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The history of quantum mechanics as this interlaces with history of quantum chemistry began essentially with the 1838 discovery of cathode rays by Michael Faraday, during the 1859-1860 winter statement of the black body radiation problem by Gustav Kirchhoff, the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete, and the 1900 quantum hypothesis by Max Planck that any energy radiating atomic system can theoretically be divided into a number of discrete ‘energy elements’ ε (epsilon) such that each of these energy elements is proportional to the frequency ν with which they each individually radiate energy, as defined by the following formula:

\epsilon = h \nu \,


where h is a numerical value called Planck’s constant. Then, in 1905, to explain the photoelectric effect (1839), i.e. that shining light on certain materials can function to eject electrons from the material, Albert Einstein postulated, as based on Planck’s quantum hypothesis, that light itself consists of individual quantum particles, which later came to be called photons (1926). The phrase "quantum mechanics" was first used in Max Born's 1924 paper "Zur Quantenmechanik". In the years to follow, this theoretical basis slowly began to be applied to chemical structure, reactivity, and bonding.

Overview

In short, in 1900, German physicist Max Planck introduced the idea that energy is quantized, in order to derive a formula for the observed frequency dependence of the energy emitted by a black body. In 1905, Einstein explained the photoelectric effect by postulating that light, or more generally all electromagnetic radiation, can be divided into a finite number of "energy quanta" that are localized points in space. From the introduction section of his March 1905 quantum paper, “On a heuristic viewpoint concerning the emission and transformation of light”, Einstein states:




This statement has been called the most revolutionary sentence written by a physicist of the twentieth century. These energy quanta later came to be called "photons", a term introduced by Gilbert N. Lewis in 1926. The idea that each photon had to consist of energy in terms of quanta was a remarkable achievement; it effectively solved the problem of black body radiation attaining infinite energy, which occurred in theory if light were to be explained only in terms of waves. In 1913, Bohr explained the spectral lines of the hydrogen atom, again by using quantization, in his paper of July 1913 On the Constitution of Atoms and Molecules.

These theories, though successful, were strictly phenomenological: during this time, there was no rigorous justification for quantization, aside, perhaps, from Henri Poincaré's discussion of Planck's theory in his 1912 paper Sur la théorie des quanta. They are collectively known as the old quantum theory.

The phrase "quantum physics" was first used in Johnston's Planck's Universe in Light of Modern Physics (1931).

In 1924, the French physicist Louis de Broglie put forward his theory of matter waves by stating that particles can exhibit wave characteristics and vice versa. This theory was for a single particle and derived from special relativity theory. Building on de Broglie's approach, modern quantum mechanics was born in 1925, when the German physicists Werner Heisenberg and Max Born developed matrix mechanics and the Austrian physicist Erwin Schrödinger invented wave mechanics and the non-relativistic Schrödinger equation as an approximation to the generalised case of de Broglie's theory. Schrödinger subsequently showed that the two approaches were equivalent.

Heisenberg formulated his uncertainty principle in 1927, and the Copenhagen interpretation started to take shape at about the same time. Starting around 1927, Paul Dirac began the process of unifying quantum mechanics with special relativity by proposing the Dirac equation for the electron. The Dirac equation achieves the relativistic description of the wavefunction of an electron that Schrödinger failed to obtain. It predicts electron spin and led Dirac to predict the existence of the positron. He also pioneered the use of operator theory, including the influential bra-ket notation, as described in his famous 1930 textbook. During the same period, Hungarian polymath John von Neumann formulated the rigorous mathematical basis for quantum mechanics as the theory of linear operators on Hilbert spaces, as described in his likewise famous 1932 textbook. These, like many other works from the founding period still stand, and remain widely used.

The field of quantum chemistry was pioneered by physicists Walter Heitler and Fritz London, who published a study of the covalent bond of the hydrogen molecule in 1927. Quantum chemistry was subsequently developed by a large number of workers, including the American theoretical chemist Linus Pauling at Caltechmarker, and John C. Slater into various theories such as Molecular Orbital Theory or Valence Theory.

Beginning in 1927, attempts were made to apply quantum mechanics to fields rather than single particles, resulting in what are known as quantum field theories. Early workers in this area included P.A.M. Dirac, W. Pauli, V. Weisskopf, and P. Jordan. This area of research culminated in the formulation of quantum electrodynamics by R.P. Feynman, F. Dyson, J. Schwinger, and S.I. Tomonaga during the 1940s. Quantum electrodynamics is a quantum theory of electrons, positrons, and the electromagnetic field, and served as a role model for subsequent quantum field theories.The theory of quantum chromodynamics was formulated beginning in the early 1960s. The theory as we know it today was formulated by Politzer, Gross and Wilczek in 1975. Building on pioneering work by Schwinger, Higgs and Goldstone, the physicists Glashow, Weinberg and Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force, for which they received the 1979 Nobel Prize in Physics.

Timeline

The following timeline shows the key steps and contributors in the precursory development of quantum mechanics and quantum chemistry:
Date Person Contribution
1900 Max Planck To explain black body radiation (1862), he suggested that electromagnetic energy could only be emitted in quantized form, i.e. the energy could only be a multiple of an elementary unit E = hν, where h is Planck's constant and ν is the frequency of the radiation.
1901 Frederick Soddy and Ernest Rutherford Discovered nuclear transmutation when they found that radioactive thorium was converting itself into radium through a process of nuclear decay.
1902 Gilbert N. Lewis To explain the octet rule (1893), he developed the “cubical atom” theory in which electrons in the form of dots were positioned at the corner of a cube and suggested that single, double, or triple “bonds” result when two atoms are held together by multiple pairs of electrons (one pair for each bond) located between the two atoms (1916).
1904 Richard Abegg Noted the pattern that the numerical difference between the maximum positive valence, such as +6 for H2SO4, and the maximum negative valence, such as -2 for H2S, of an element tends to be eight (Abegg's rule).
1905 Albert Einstein Determines the equivalence of matter and energy.
1905 Albert Einstein First to explain the effects of Brownian motion as caused by the kinetic energy (i.e., movement) of atoms, which was subsequently, experimentally verified by Jean Baptiste Perrin, thereby settling the century-long dispute about the validity of John Dalton's atomic theory.
1905 Albert Einstein Publishes his Special Theory of Relativity.
1905 Albert Einstein Explained the photoelectric effect (1839), i.e. that shining light on certain materials can function to eject electrons from the material, he postulated, as based on Planck’s quantum hypothesis (1900), that light itself consists of individual quantum particles (photons).
1907 Ernest Rutherford To test the plum pudding model (1904), he fired, positively-charged, alpha particles at gold foil and noticed that some bounced back thus showing that an atom has a small-sized positively charged atomic nucleus at its center.
1909 Geoffrey Ingram Taylor Demonstrated that interference patters of light were generated even when the light energy introduced consisted of only one photon. This discovery of the wave-particle duality of matter and energy was fundamental to the later development of quantum field theory.
1909 and 1916 Albert Einstein Showed that, if Planck's law of black-body radiation is accepted, the energy quanta must also carry momentum p = h / λ, making them full-fledged particles.
1911 Lise Meitner and Otto Hahn Performed an experiment that showed that the energies of electrons emitted by beta decay had a continuous rather than discrete spectrum. This was in apparent contradiction to the law of conservation of energy, as it appeared that energy was lost in the beta decay process. A second problem was that the spin of the Nitrogen-14 atom was 1, in contradiction to the Rutherford prediction of ½. These anomalies were later explained by the discoveries of the neutrino and the neutron.
1912 Victor Hess Discovers the existence of cosmic radiation.
1912 Henri Poincaré Published an influential mathematical argument in support of the essential nature of energy quanta.
1913 Robert Andrews Millikan Publishes the results of his "oil drop" experiment, in which he precisely determines the electric charge of the electron. Determination of the fundamental unit of electric charge made it possible to calculate the Avogadro constant (which is the number of atoms or molecules in one mole of any substance) and thereby to determine the atomic weight of the atoms of each element.
1913 Johannes Stark and Antonino Lo Surdo Independently discovered the shifting and splitting of the spectral lines of atoms and molecules due to the presence of the light source in an external static electric field.
1913 Niels Bohr To explain the Rydberg formula (1888), which correctly modeled the light emission spectra of atomic hydrogen, Bohr hypothesized that negatively charged electrons revolve around a positively charged nucleus at certain fixed “quantum” distances and that each of these “spherical orbits” has a specific energy associated with it such that electron movements between orbits requires “quantum” emissions or absorptions of energy.
1915 Albert Einstein First presents to the Prussian Academy of Science what are now known as the Einstein field equations. These equations specify how the geometry of space and time is influenced by whatever matter is present, and form the core of Einstein's General Theory of Relativity. Although this theory is not directly applicable to quantum mechanics, theorists of quantum gravity seek to reconcile them.
1916 Arnold Sommerfeld To account for the Zeeman effect (1896), i.e. that atomic absorption or emission spectral lines change when the light source is subjected to a magnetic field, he suggested there might be “elliptical orbits” in atoms in addition to spherical orbits.
1918 Ernest Rutherford Noticed that, when alpha particles were shot into nitrogen gas, his scintillation detectors showed the signatures of hydrogen nuclei. Rutherford determined that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggested that the hydrogen nucleus, which was known to have an atomic number of 1, was an elementary particle, which he decided must be the protons hypothesized by Eugen Goldstein.
1919 Irving Langmuir Building on the work of Lewis (1916), he coined the term "covalence" and postulated that coordinate covalent bonds occur when two electrons of a pair of atoms come from both atoms and are equally shared by them, thus explaining the fundamental nature of chemical bonding and molecular chemistry.
1922 Arthur Compton Found that X-ray wavelengths increase due to scattering of the radiant energy by "free electrons". The scattered quanta have less energy than the quanta of the original ray. This discovery, known as the "Compton effect," or "Compton scattering" demonstrates the "particle" concept of electromagnetic radiation.
1922 Otto Stern and Walther Gerlach Stern-Gerlach experiment detects discrete values of angular momentum for atoms in the ground state passing through an inhomogeneous magnetic field leading to the discovery of the spin of the electron.
1923 Louis De Broglie Postulated that electrons in motion are associated with waves the lengths of which are given by Planck’s constant h divided by the momentum of the mv = p of the electron: λ = h / mv = h / p.
1924 Satyendra Nath Bose His work on quantum mechanics provides the foundation for Bose-Einstein statistics, the theory of the Bose-Einstein condensate, and the discovery of the boson.
1925 Friedrich Hund Outlined the “rule of maximum multiplicity” which states that when electrons are added successively to an atom as many levels or orbits are singly occupied as possible before any pairing of electrons with opposite spin occurs and made the distinction that the inner electrons in molecules remained in atomic orbitals and only the valence electrons needed to be in molecular orbitals involving both nuclei.
1925 Werner Heisenberg Developed the matrix mechanics formulation of Quantum Mechanics.
1925 Wolfgang Pauli Outlined the “Pauli exclusion principle” which states that no two identical fermions may occupy the same quantum state simultaneously.
1926 Gilbert Lewis Coined the term photon, which he derived from the Greek word for light, φως (transliterated phôs).
1926 Erwin Schrödinger Used De Broglie’s electron wave postulate (1924) to develop a “wave equation” that represents mathematically the distribution of a charge of an electron distributed through space, being spherically symmetric or prominent in certain directions, i.e. directed valence bonds, which gave the correct values for spectral lines of the hydrogen atom.
1927 Charles Drummond Ellis (along with James Chadwick and colleagues) Finally established clearly that the beta decay spectrum is in fact continuous and not discrete, posing a problem that would later by solved by theorizing (and later discovering) the existence of the neutrino.
1927 Walter Heitler Used Schrödinger’s wave equation (1926) to show how two hydrogen atom wavefunctions join together, with plus, minus, and exchange terms, to form a covalent bond.
1927 Robert Mulliken In 1927 Mulliken worked, in coordination with Hund, to develop a molecular orbital theory where electrons are assigned to states that extend over an entire molecule and, in 1932, introduced many new molecular orbital terminologies, such as σ bond, π bond, and δ bond.
1928 Paul Dirac In the Dirac equations, Paul Dirac integrated the principal of special relativity with quantum electrodynamics and hypothesized the existence of the positron.
1928 Linus Pauling Outlined the nature of the chemical bond in which he used Heitler’s quantum mechanical covalent bond model (1927) to outline the quantum mechanical basis for all types of molecular structure and bonding and suggested that different types of bonds in molecules can become equalized by rapid shifting of electrons, a process called “resonance” (1931), such that resonance hybrids contain contributions from the different possible electronic configurations.
1929 John Lennard-Jones Introduced the linear combination of atomic orbitals approximation for the calculation of molecular orbitals.
1930 Wolfgang Pauli In a famous letter, Pauli suggested that, in addition to electrons and protons, atoms also contained an extremely light neutral particle which he called the "neutron." He suggested that this "neutron" was also emitted during beta decay and had simply not yet been observed. Later it was determined that this particle was actually the almost massless neutrino.
1931 Walther Bothe and Herbert Becker Found that if the very energetic alpha particles emitted from polonium fell on certain light elements, specifically beryllium, boron, or lithium, an unusually penetrating radiation was produced. At first this radiation was thought to be gamma radiation, although it was more penetrating than any gamma rays known, and the details of experimental results were very difficult to interpret on this basis. Some scientists began to hypothesize the possible existence of another fundamental, atomic particle.
1931 Enrico Fermi Renamed Pauli's "neutron" to neutrino in order to distinguish it from the then-hypothetical possibility of a much more massive neutron.
1932 Irène Joliot-Curie and Frédéric Joliot Showed that if the unknown radiation generated by alpha particles fell on paraffin or any other hydrogen-containing compound, it ejected protons of very high energy. This was not in itself inconsistent with the proposed gamma ray nature of the new radiation, but detailed quantitative analysis of the data became increasingly difficult to reconcile with such a hypothesis.
1932 James Chadwick Performed a series of experiments showing that the gamma ray hypothesis for the unknown radiation produced by alpha particles was untenable, and that the new particles must be the neutrons hypothesized by Enrico Fermi. Chadwick suggested that, in fact, the new radiation consisted of uncharged particles of approximately the same mass as the proton, and he performed a series of experiments verifying his suggestion.
1932 Werner Heisenberg Applied perturbation theory to the two-electron problem and showed how resonance arising from electron exchange could explain exchange forces.
1932 Mark Oliphant Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, fusion of light nuclei (hydrogen isotopes) was first observed by Oliphant in 1932. The steps of the main cycle of nuclear fusion in stars were subsequently worked out by Hans Bethe throughout the remainder of that decade.
1932 Carl D. Anderson Experimentally proves the existence of the positron.
1933 Leó Szilárd First theorized the concept of a nuclear chain reaction. He filed a patent for his idea of a simple nuclear reactor the following year.
1934 Enrico Fermi Published a very successful model of beta decay in which neutrinos were produced.
1934 Enrico Fermi Studies the effects of bombarding uranium isotopes with neutrons.
1934 N.N.Semyonov Develops the total quantitative chain chemical reaction theory. The idea of the chain reaction, developed by Semyonov, is the basis of various high technologies using the incineration of gas mixtures. The idea was also used for the description of the nuclear reaction.
1935 Hideki Yukawa Published his hypothesis of the Yukawa Potential and predicted the existence of the pion, stating that such a potential arises from the exchange of a massive scalar field, such as would be found in the field of the pion. Prior to Yukawa's paper, it was believed that the scalar fields of the fundamental forces necessitated massless particles.
1936 Carl D. Anderson Discovered muons while he studied cosmic radiation.
1937 Carl Anderson Experimentally proves the existence of the pion.
1938 Charles Coulson Made the first accurate calculation of a molecular orbital wavefunction with the hydrogen molecule.
1938 Otto Hahn, Fritz Strassmann, Lise Meitner, and Otto Robert Frisch Hahn and Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons. Simultaneously, they communicated these results to Meitner. Meitner, and her nephew Frisch, correctly interpreted these results as being nuclear fission. Frisch confirmed this experimentally on 13 January 1939.
1939 Leó Szilárd and Enrico Fermi Discovered neutron multiplication in uranium, proving that a chain reaction was indeed possible.
1942 Kan-Chang Wang First proposed the use of beta capture to experimentally detect neutrinos.
1942 Enrico Fermi Created the first artificial self-sustaining nuclear chain reaction, called Chicago Pile-1 (CP-1), in a racquets court below the bleachers of Stagg Field at the University of Chicago on December 2, 1942.
1945 Manhattan Project First nuclear fission explosion.
1947 G. D. Rochester and C. C. Butler Published two cloud chamber photographs of cosmic ray-induced events, one showing what appeared to be a neutral particle decaying into two charged pions, and one which appeared to be a charged particle decaying into a charged pion and something neutral. The estimated mass of the new particles was very rough, about half a proton's mass. More examples of these "V-particles" were slow in coming, and they were soon given the name kaons.
1948 Sin-Itiro Tomonaga and Julian Schwinger Independently introduced perturbative renormalization as a method of correcting the original Lagrangian of a quantum field theory so as to eliminate an infinite series of counterterms that would otherwise result.
1948 Richard Feynman Stated the path integral formulation of quantum mechanics.
1949 Freeman Dyson Determined the equivalence of the formulations of quantum electrodynamics that existed by that time — Richard Feynman's diagrammatic path integral formulation and the operator method developed by Julian Schwinger and Sin-Itiro Tomonaga. A by-product of that demonstration was the invention of the Dyson series.
1951 Clemens C. J. Roothaan and George G. Hall Derived the Roothaan-Hall equations, putting rigorous molecular orbital methods on a firm basis.
1952 Manhattan Project First explosion of a thermonuclear bomb.
1954 Chen Ning Yang and Robert Mills Derived a gauge theory for nonabelian groups, leading to the successful formulation of both electroweak unification and quantum chromodynamics.
1955 and 1956 Murray Gell-Mann and Kazuhiko Nishijima Independently derived the Gell-Mann–Nishijima formula, which relates the baryon number B, the strangeness S, and the isospin Iz of hadrons to the charge Q, eventually leading to the systematic categorization of hadrons and, ultimately, the Quark Model of hadron composition.
1956 P. Kuroda Predicted that self-sustaining nuclear chain reactions should occur in natural uranium deposits.
1956 Clyde L. Cowan and Frederick Reines Experimentally proved the existence of the neutrino.
1957 William Alfred Fowler, Margaret Burbidge, Geoffrey Burbidge, and Fred Hoyle In their 1957 paper Synthesis of the Elements in Stars, they explained how the abundances of essentially all but the lightest chemical elements could be explained by the process of nucleosynthesis in stars.
1961 Clauss Jönsson Performed Young's double-slit experiment (1909) for the first time with a particle other than photons by using electrons and with similar results, confirming that massive particles also behaved according to the wave-particle duality that is a fundamental principal of quantum field theory.
1961 Sheldon Lee Glashow Extended the electroweak unification models developed by Julian Schwinger by including a short range neutral current, the Z0. The resulting symmetry structure that Glashow proposed, SU(2) X U(1), formed the basis of the accepted theory of the electroweak interactions.
1962 Leon M. Lederman, Melvin Schwartz and Jack Steinberger Showed that more than one type of neutrino exists by detecting interactions of the muon neutrino (already hypothesised with the name "neutretto")
1962 Murray Gell-Mann and Yuval Ne'eman Independently classified the hadrons according to a system that Gell-Mann called the "Eightfold Way," and which ultimately led to the quark model (1964) of hadron composition.
1962 Jeffrey Goldstone, Yoichiro Nambu, Abdus Salam, and Steven Weinberg Developed what is now known as Goldstone's Theorem, in which it was proved that, if there is continuous symmetry transformation under which the Lagrangian is invariant, then either the vacuum state is also invariant under the transformation, or there must exist spinless particles of zero mass, thereafter called Nambu-Goldstone bosons.
1963 Nicola Cabibbo Developed the mathematical matrix by which the first two (and ultimately three) generations of quarks could be predicted.
1964 Murray Gell-Mann and George Zweig Independently proposed the quark model of hadrons, predicting the arbitrarily named up, down, and strange quarks. Gell-Mann is credited with coining the term "quark," which he found in James Joyce's book Finnegans Wake.
1964 François Englert, Robert Brout, Peter Higgs, Gerald Guralnik, C. R. Hagen, and Tom Kibble Postulated that a fundamental quantum field, now called the Higgs field, permeates space and, by way of the Higgs mechanism, provides mass to all the elementary subatomic particles that interact with it. While the Higgs field is postulated to confer mass on quarks and leptons, it represents only a tiny portion of the masses of other subatomic particles, such as protons and neutrons. In these, gluons that bind quarks together confer most of the particle mass. The Higgs mechanism, which gives mass to vector bosons, was theorized in 1964 by François Englert and Robert Brout. In October of the same year, Peter Higgs, working from the ideas of Philip Anderson reached the same conclusions; and, independently, by Gerald Guralnik, C. R. Hagen, and Tom Kibble, who worked out the results by the spring of 1963.
1964 Sheldon Lee Glashow and James Bjorken Predicted the existence of the charm quark. The addition was proposed because it allowed for a better description of the weak interaction (the mechanism that allows quarks and other particles to decay), equalized the number of known quarks with the number of known leptons, and implied a mass formula that correctly reproduced the masses of the known mesons.
1967 Steven Weinberg and Abdus Salam Published a paper in which he described Yang-Mills Theory using the SU(2) X U(1) supersymmetry group, thereby yielding a mass for the W particle of the Weak Interaction via spontaneous symmetry breaking.
1968 Stanford Universitymarker Deep inelastic scattering experiments at the Stanford Linear Accelerator Centermarker (SLAC) showed that the proton contained much smaller, point-like objects and was therefore not an elementary particle. Physicists at the time were reluctant to identify these objects with quarks, instead calling them "partons" — a term coined by Richard Feynman. The objects that were observed at SLAC would later be identified as up and down quarks. Nevertheless, "parton" remains in use as a collective term for the constituents of hadrons (quarks, antiquarks, and gluons). The strange quark's existence was indirectly validated by the SLAC's scattering experiments: not only was it a necessary component of Gell-Mann and Zweig's three-quark model, but it provided an explanation for the kaon (K) and pion (π) hadrons discovered in cosmic rays in 1947.
1970 Sheldon Lee Glashow, John Iliopoulos and Luciano Maiani Presented further reasoning for the existence of the as-yet undiscovered charm quark.
1971 Martinus J. G. Veltman and Gerardus 't Hooft Showed that, if the symmetries of Yang-Mills Theory were to be broken according to the method suggested by Peter Higgs, then Yang-Mills theory can be renormalized. The renormalization of Yang-Mills Theory predicted the existence of a massless particle, called the gluon, which could explain the nuclear Strong Force. It also explained how the particles of the Weak Interaction, the W and Z bosons, obtained their mass via spontaneous symmetry breaking and the Yukawa interaction.
1972 Francis Perrin Discovered the existence of "natural nuclear fission reactors" in uranium deposits in Oklomarker, Gabonmarker, where analysis of isotope ratios demonstrated that self-sustaining, nuclear chain reactions had occurred. The conditions under which a natural nuclear reactor could exist were predicted in 1956 by P. Kuroda.
1973 Makoto Kobayashi and Toshihide Maskawa Noted that the experimental observation of CP violation could be explained if an additional pair of quarks existed. The two new quarks were eventually named top and bottom.
1974 Pier Giorgio Merli Performed Young's double-slit experiment (1909) using a single electron with similar results, confirming the existence of quantum fields for massive particles.
1974 Burton Richter and Samuel Ting Charm quarks were produced almost simultaneously by two teams in November 1974 (see November Revolution) — one at SLACmarker under Burton Richter, and one at Brookhaven National Laboratorymarker under Samuel Ting. The charm quarks were observed bound with charm antiquarks in mesons. The two discovering parties had independently assigned the discovered meson two different symbols, J and ψ; thus, it became formally known as the J/ψ meson. The discovery finally convinced the physics community of the quark model's validity.
1975 Martin Lewis Perl With his colleagues at the SLACmarkerLBLmarker group, he detected the tauon in a series of experiments between 1974 and 1977.
1977 Leon Lederman Observed the bottom quark with his team at Fermilabmarker. This discovery was a strong indicator of the top quark's existence: without the top quark, the bottom quark would have been without a partner that was required by the mathematics of the theory.
1983 Carlo Rubbia and Simon van der Meer Unambiguous signals of W particles were seen in January 1983 during a series of experiments conducted by Carlo Rubbia and Simon van der Meer at the Super Proton Synchrotronmarker. The actual experiments were called UA1 (led by Rubbia) and UA2 (led by Peter Jenni), and were the collaborative effort of many people. Simon van der Meer was the driving force on the use of the accelerator. UA1 and UA2 found the Z particle a few months later, in May 1983.
1995 Fermilabmarker The top quark was finally observed by a team at Fermilab. It had a mass much greater than had been previously expected — almost as great as a gold atom.
1995 Eric Cornell, Carl Wieman and Wolfgang Ketterle The first "pure" Bose–Einstein condensate was created by Eric Cornell, Carl Wieman, and co-workers at JILA. They did this by cooling a dilute vapor consisting of approximately two thousand rubidium-87 atoms to below 170 nK using a combination of laser cooling and magnetic evaporative cooling. About four months later, an independent effort led by Wolfgang Ketterle at MITmarker created a condensate made of sodium-23. Ketterle's condensate had about a hundred times more atoms, allowing him to obtain several important results such as the observation of quantum mechanical interference between two different condensates.
2000 CERNmarker CERN scientists publish experimental results in which they claim to have observed indirect evidence of the existence of a quark-gluon plasma, which they call a "new state of matter."


Founding experiments



See also



References

  1. F. J. Dyson, Phys. Rev. 75, 486, 1736 (1949)
  2. The Davisson-Germer experiment, which demonstrates the wave nature of the electron


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