Friedrich Hund

Friedrich Hund

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Friedrich Hermann Hund (4 February 1896 - 31 March 1997) was a German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 from Karlsruhe
Karlsruhe
The City of Karlsruhe is a city in the southwest of Germany, in the state of Baden-Württemberg, located near the French-German border.Karlsruhe was founded in 1715 as Karlsruhe Palace, when Germany was a series of principalities and city states...

 known for his work on atoms and molecules.

Hund worked at the Universities of Rostock
University of Rostock
The University of Rostock is the university of the city Rostock, in the German state of Mecklenburg-Vorpommern.Founded in 1419, it is the oldest and largest university in continental northern Europe and the Baltic Sea area...

, Leipzig
University of Leipzig
The University of Leipzig , located in Leipzig in the Free State of Saxony, Germany, is one of the oldest universities in the world and the second-oldest university in Germany...

, Jena, Frankfurt am Main, and Göttingen.

Hund worked with such prestigious physicists as Schrödinger
Erwin Schrödinger
Erwin Rudolf Josef Alexander Schrödinger was an Austrian physicist and theoretical biologist who was one of the fathers of quantum mechanics, and is famed for a number of important contributions to physics, especially the Schrödinger equation, for which he received the Nobel Prize in Physics in 1933...

, Dirac
Paul Dirac
Paul Adrien Maurice Dirac, OM, FRS was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...

, Heisenberg
Werner Heisenberg
Werner Karl Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...

, Max Born
Max Born
Max Born was a German-born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...

, and Walter Bothe. At that time, he was Born's assistant, working with quantum interpretation of band spectra of diatomic molecules.
After his studies of mathematics, physics, and geography in Marburg and Göttingen, he worked as a private lecturer for theoretical physics in Göttingen (1925), professor in Rostock (1927), Leipzig (1929), Jena (1946), Frankfurt/Main (1951) and from 1957 again in Göttingen. Additionally, he stayed in Copenhagen (1926) with Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

 and lectured on the atom at Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 in Cambridge, Massachusetts (1928). He published more than 250 papers and essays in total. Hund made pivotal contributions to quantum theory - especially concerning the structure of the atom and of molecular spectra.

In fact, Robert S. Mulliken
Robert S. Mulliken
Robert Sanderson Mulliken was an American physicist and chemist, primarily responsible for the early development of molecular orbital theory, i.e. the elaboration of the molecular orbital method of computing the structure of molecules. Dr. Mulliken received the Nobel Prize for chemistry in 1966...

, who was awarded the 1966 Nobel Prize in chemistry for molecular orbital theory, always proclaimed the great influence Hund's work had on his own and that he would have gladly shared the Nobel prize with Hund. In recognition of the importance of Hund's contributions, MO theory is often referred to as the Hund-Mulliken MO theory. Hund's rule of maximum multiplicity
Hund's rule of Maximum Multiplicity
Hund's Rule of Maximum Multiplicity is an observational rule which states that a greater total spin state usually makes the resulting atom more stable. Accordingly, it can be taken that if two or more orbitals of equal energy are available, electrons will occupy them singly before filling them in...

 is another eponym and, in 1926, Hund discovered the so-called tunnel effect or quantum tunnelling
Quantum tunnelling
Quantum tunnelling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an essential role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the sun, and has important...

.

The Hund's cases, which are particular regimes in molecular angular momentum coupling
Angular momentum coupling
In quantum mechanics, the procedure of constructing eigenstates of total angular momentum out of eigenstates of separate angular momenta is called angular momentum coupling. For instance, the orbit and spin of a single particle can interact through spin-orbit interaction, in which case the...

, and Hund's rules, which govern electron configuration
Electron configuration
In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons of an atom, a molecule, or other physical structure...

s, are important in spectroscopy
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...

 and quantum chemistry
Quantum chemistry
Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems...

. In chemistry, the first rule, Hund's rule of maximum multiplicity
Hund's rule of Maximum Multiplicity
Hund's Rule of Maximum Multiplicity is an observational rule which states that a greater total spin state usually makes the resulting atom more stable. Accordingly, it can be taken that if two or more orbitals of equal energy are available, electrons will occupy them singly before filling them in...

, is especially important and is often referred to as simply Hund's Rule.

On the occasion of his 100th birthday, the book: Friedrich Hund: Geschichte der physikalischen Begriffe [History of Physical Concepts] (Heidelberg, Berlin, Oxford), Spektrum, Akademie Verlag 1996, ISBN 3-8274-0083-X was published. A review was also written by Werner Kutzelnigg
Werner Kutzelnigg
Werner Kutzelnigg, born on September 10, 1933 in Vienna, Austria, is a prominent theoretical chemist. He is now emeritus Professor in the Chemistry Faculty, Ruhr-Universität Bochum, Germany....

.

Besides many different honors bestowed upon him, Friedrich Hund became an honorary citizen of Jena/Saale, and a street in Jena was named after him. Since June 2004, a part of the new building of the Physics Department was given the Friedrich-Hund-Platz 1 address. The same name was chosen for the Institute for Theoretical Physics at the University of Göttingen.

He was a member of the International Academy of Quantum Molecular Science
International Academy of Quantum Molecular Science
The International Academy of Quantum Molecular Science is an international scientific learned society covering all applications of quantum theory to chemistry and chemical physics. It was created in Menton in 1967. The founding members were Raymond Daudel, Per-Olov Löwdin, Robert G. Parr, John...

.

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