History of quantum mechanics



  The history of quantum mechanics as this interlaces with history of Max Planck that any energy radiating atomic system can theoretically be divided into a number of discrete ‘energy elements’ ε 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 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 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:

“ According to the assumption to be contemplated here, when a light ray is spreading from a point, the energy is not distributed continuously over ever-increasing spaces, but consists of a finite number of energy quanta that are localized in points in space, move without dividing, and can be absorbed or generated only as a whole. ”

This statement has been called the most revolutionary sentence written by a physicist of the twentieth century.[1] These energy quanta later came to be called "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: there was no rigorous justification for quantization (aside, perhaps, for 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 (see Hanle (1977)). 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 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 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, 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 Wilzcek in 1975. Building on pioneering work by Schwinger, Higgs, Goldstone, Glashow, Weinberg and Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force.

Timeline

The following timeline shows the key steps and contributors in the precursory development of quantum mechanics and quantum chemistry:

Date Person Contribution
1771 Luigi Galvani Noted that the muscles of dead frogs twitched when struck by a spark, to which he referred to as “animal electricity.”
1800 Alessandro Volta Invented the voltaic pile, or "battery", specifically to disprove Galvani's animal electricity theory (1771).
1838 Michael Faraday Using Volta's battery (1800), he discovered “cathode rays” when, during an experiment, he passed current through a rarefied air filled glass tube and noticed a strange light arc starting at the cathode (negative electrode).
1852 Edward Frankland Initiated the theory of valency by proposing that each element has a specific “combining power”, e.g. some elements such as nitrogen tend to combine with three other elements (e.g. NO3) while others may tend to combine with five (e.g. PO5), and that each element strives to fulfill its combining power (valency) quota so as to satisfy their affinities.
1859 Gustav Kirchhoff Stated the "black body problem", i.e. how does the intensity of the temperature of the body?
1877 Ludwig Boltzman Suggested that the energy states of a physical system could be discrete.
1879 William Crookes Showed that cathode rays (1838), unlike light rays, can be bent in a magnetic field.
1885 Johann Balmer Discovered that the four visible lines of the hydrogen spectrum could be assigned integers in a series
1888 Johannes Rydberg Modified Balmer formula to include the other series of lines to produce Rydberg formula
1891 Alfred Werner Proposed a theory of affinity and valence in which affinity is an attractive force issuing from the center of the atom which acts uniformly from there towards all parts of the spherical surface of the central atom.
1892 Heinrich Hertz Showed that cathode rays (1838) could pass through thin sheets of gold foil and produce appreciable luminosity on glass behind them.
1896 Henri Becquerel Discovered “gamma particles (neutral charge).
1897 Joseph Thomson Showed that cathode rays (1838) bend under the influence of both an electric field and a magnetic field and to explain this he suggested that cathode rays are negatively charged subatomic electrical particles or “corpuscles” (plum pudding model" in which atoms have a positively charged amorphous mass (pudding) as a body embedded with negatively charged electrons (raisins) scattered throughout in the form of non-random rotating rings.
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.
1902 Gilbert N. Lewis To explain the 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 To explain the light itself consists of individual quantum particles (photons).
1907 Ernest Rutherford To test the plum pudding model (1904), he fired, positively-charged, atomic nucleus at its center.
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.
1916 Arnold Sommerfeld To account for the Zeeman effect (1896), i.e. that atomic absorption or emission spectral lines change when the light is first shinned through a magnetic field, he suggesting that there might be “elliptical orbits” in atoms in addition to spherical orbits.
1919 Irving Langmuir Building on the work of Lewis (1916), he coined the term "covalence" and postulated that coordinate covalent bonds occur when the electrons of a pair come from the same atom.
1922 Stern & 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 electron: λ = h / mv = h / p.
1925 Friedrich Hund Outlined the “valence electrons needed to be in molecular orbitals involving both nuclei.
1925 Wolfgang Pauli Outlined the “Pauli exclusion principle” which states that no two identical fermions may occupy the same quantum state simultaneously.
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 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 δ bond.
1928 Linus Pauling Outlined the nature of the 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.
1932 Werner Heisenberg Applied resonance arising from electron exchange could explain exchange forces.
1938 Charles Coulson Made the first accurate calculation of a molecular orbital wavefunction with the hydrogen molecule.
1951 Clemens C. J. Roothaan and George G. Hall Derived the Roothaan-Hall equations, putting rigorous molecular orbital methods on a firm basis.

Founding experiments

  • Thomas Young's double-slit experiment demonstrating the wave nature of light (c1805)
  • radioactivity (1896)
  • Joseph John Thomson's cathode ray tube experiments (discovers the electron and its negative charge) (1897)
  • The study of black body radiation between 1850 and 1900, which could not be explained without quantum concepts.
  • The photoelectric effect: Einstein explained this in 1905 (and later received a Nobel prize for it) using the concept of photons, particles of light with quantized energy
  • Robert Millikan's electric charge occurs as quanta (whole units), (1909)
  • atom which suggested that the mass and positive charge of the atom are almost uniformly distributed. (1911)
  • Otto Stern and Walther Gerlach conduct the Stern-Gerlach experiment, which demonstrates the quantized nature of particle spin (1920)
  • Clinton Davisson and Lester Germer demonstrate the wave nature of the Electron diffraction experiment (1927)
  • Clyde L. Cowan and Frederick Reines confirm the existence of the neutrino in the neutrino experiment (1955)
  • Claus Jönsson`s double-slit experiment with electrons (1961)
  • The Hall effect has allowed for the definition of a new practical standard for electrical resistance and for an extremely precise independent determination of the fine structure constant.
  • The experimental verification of quantum entanglement by Alain Aspect in 1982.

References

  1. ^ Folsing, Albrecht (1997). Albert Einstein: A Biography. trans. Ewald Osers, Viking. 
  2. ^ The Davisson-Germer experiment, which demonstrates the wave nature of the electron
  • Hanle, P.A. (1977) Erwin Schrodinger's Reaction to Louis de Broglie's Thesis on the Quantum Theory. Isis, Vol. 68, No. 4 (Dec., 1977), pp. 606-609

See also
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "History_of_quantum_mechanics". A list of authors is available in Wikipedia.