Helmut Hönl (10 February 1903– 29 March 1981) was a
German
German(s) may refer to:
* Germany, the country of the Germans and German things
**Germania (Roman era)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizenship in Germany, see also Ge ...
theoretical physicist
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict natural phenomena. This is in contrast to experimental physics, which uses experi ...
who made contributions to
quantum mechanics
Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
and the understanding of atomic and molecular structure.
Biography
Helmut Hönl was born in 1903 in
Mannheim
Mannheim (; Palatine German language, Palatine German: or ), officially the University City of Mannheim (), is the List of cities in Baden-Württemberg by population, second-largest city in Baden-Württemberg after Stuttgart, the States of Ger ...
,
German Empire
The German Empire (),; ; World Book, Inc. ''The World Book dictionary, Volume 1''. World Book, Inc., 2003. p. 572. States that Deutsches Reich translates as "German Realm" and was a former official name of Germany. also referred to as Imperia ...
.
From 1921 to circa 1923, Hönl studied at the
University of Heidelberg
Heidelberg University, officially the Ruprecht Karl University of Heidelberg (; ), is a public university, public research university in Heidelberg, Baden-Württemberg, Germany. Founded in 1386 on instruction of Pope Urban VI, Heidelberg is List ...
and the
University of Göttingen
The University of Göttingen, officially the Georg August University of Göttingen (, commonly referred to as Georgia Augusta), is a Public university, public research university in the city of Göttingen, Lower Saxony, Germany. Founded in 1734 ...
, followed by the
University of Munich
The Ludwig Maximilian University of Munich (simply University of Munich, LMU or LMU Munich; ) is a public university, public research university in Munich, Bavaria, Germany. Originally established as the University of Ingolstadt in 1472 by Duke ...
, where he studied under
Arnold Sommerfeld
Arnold Johannes Wilhelm Sommerfeld (; 5 December 1868 – 26 April 1951) was a German Theoretical physics, theoretical physicist who pioneered developments in Atomic physics, atomic and Quantum mechanics, quantum physics, and also educated and ...
. He was granted his doctor of philosophy in 1926. In 1929, he became assistant to
Paul Peter Ewald at the
Stuttgart Technische Hochschule until 1933, after which he was a
Privatdozent
''Privatdozent'' (for men) or ''Privatdozentin'' (for women), abbreviated PD, P.D. or Priv.-Doz., is an academic title conferred at some European universities, especially in German-speaking countries, to someone who holds certain formal qualifi ...
. In 1940 he became extraordinary professor at the
University of Erlangen
A university () is an institution of tertiary education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase , which roughly means "community of teachers and scholars". Univ ...
and 1943 ordinary professor for theoretical physics at the
University of Freiburg
The University of Freiburg (colloquially ), officially the Albert Ludwig University of Freiburg (), is a public university, public research university located in Freiburg im Breisgau, Baden-Württemberg, Germany. The university was founded in 1 ...
, where he became
emeritus
''Emeritus/Emerita'' () is an honorary title granted to someone who retires from a position of distinction, most commonly an academic faculty position, but is allowed to continue using the previous title, as in "professor emeritus".
In some c ...
in 1971.
Research
Before acquiring his doctorate at Munich, Hönl performed seminal research which contributed to the advancement of quantum mechanics and the understanding of atomic and molecular structure and spectra. Some of his work was done in collaboration with
Fritz London
Fritz Wolfgang London (March 7, 1900 – March 30, 1954) was a German born physicist and professor at Duke University. His fundamental contributions to the theories of chemical bonding and of intermolecular forces (London dispersion forces) are to ...
. Other researchers independently made similar findings as his work research the intensity of
Zeeman effect
The Zeeman effect () is the splitting of a spectral line into several components in the presence of a static magnetic field. It is caused by the interaction of the magnetic field with the magnetic moment of the atomic electron associated with ...
spectral lines. Both Hönl and
Samuel Goudsmit
Samuel Abraham Goudsmit (July 11, 1902 – December 4, 1978) was a Dutch-American physicist famous for jointly proposing the concept of electron spin with George Eugene Uhlenbeck in 1925.
Life and career
Goudsmit was born in The Hague, Ne ...
and
Ralph de Laer Kronig published results in 1925. Their work was promptly put into use. In the
first paper of the trilogy which launched the
matrix mechanics
Matrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925. It was the first conceptually autonomous and logically consistent formulation of quantum mechanics. Its account of quantum ...
formulation of quantum theory in 1925,
Werner Heisenberg
Werner Karl Heisenberg (; ; 5 December 1901 – 1 February 1976) was a German theoretical physicist, one of the main pioneers of the theory of quantum mechanics and a principal scientist in the German nuclear program during World War II.
He pub ...
, a former student of Sommerfeld, working with
Max Born
Max Born (; 11 December 1882 – 5 January 1970) was a German-British theoretical physicist 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 ...
at the University of Göttingen, used the work of Hönl, Kronig, and Goudsmit, referring to it as the “Goudsmit–Kronig–Hönl formula.”
At this time, there were three centers of development for quantum mechanics and the interpretation of atomic and molecular structure, based on atomic and molecular
spectroscopy
Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum.
Spectro ...
, especially the
Sommerfeld-Bohr model: the Theoretical Physics Institute at the University of Munich, under Sommerfeld, the Institute of Theoretical Physics at the University of Göttingen, under Born, and the Institute of Theoretical Physics, under
Niels Bohr
Niels Henrik David Bohr (, ; ; 7 October 1885 – 18 November 1962) was a Danish theoretical physicist who made foundational contributions to understanding atomic structure and old quantum theory, quantum theory, for which he received the No ...
. These three institutes effectively formed a consortium for the exchange of assistants and researchers. Furthermore, with Sommerfeld educating such capable physicists, when they were called to other facilities, they effectively became extensions of Sommerfeld’s Institute of Theoretical Physics.
This was the case with Hönl when he went to the Stuttgart Technische Hochschule (STH) to work with
Paul Peter Ewald, who received his Ph.D. under Sommerfeld and became ordinarius professor of theoretical physics at STH in 1921. At Stuttgart, Ewald and Hönl worked on the quantum theory atomic and molecular structure and
solid-state physics
Solid-state physics is the study of rigid matter, or solids, through methods such as solid-state chemistry, quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state phy ...
. They developed a theoretical model of electron densities and the atomic scattering factor in solids. Their work has been referenced in the literature as the Ewald-Hönl-Brill model (after the German physicist
Rudolf Brill[R. Brill, H. G. Grimm, C. Herman, and C. Peters ''Annalen der Physik'' 34 (1939) 393.]).
Selected literature
*Arnold Sommerfeld and Helmut Hönl ''Über die Intensität der Multiplett-Linien'', ''Sitzungsberichte der Preußischen Akademie der Wissenschaften. Physikalisch-mathematische Klasse.'' 141-161 (1925) as cited i
Arnold Sommerfeld Bibliography– Sommerfeld Project.
*Helmut Hönl “The intensity of Zeeman components” (Translated from the German) ''Zeitschrift für Physik'' 31 340-354 (1925)
*Helmut Hönl and Fritz London “The intensities of the band lines” (Translated from the German) ''Zeitschrift für Physik'' 33 803-809 (1925)
*Helmut Hönl “The intensity problem of spectral lines” (Translated from the German) ''Annalen der Physik'' 79 273-323 (1926)
*P. P. Ewald and H. Hönl "The x-ray interferences in diamond as a wave-mechanical problem. Part I." (English translation from the German) ''Annalen der Physik'' 25 (4): 281-308 (1936)
*P. P. Ewald and H. Hönl "X-ray interference in diamonds as problem of wave mechanics. Part II Analysis of linear atomic chains." (English translation from the German) ''Annalen der Physik'' 26 (8): 673-696 (1936)
References
*
Mehra, Jagdish, and
Helmut Rechenberg ''The Historical Development of Quantum Theory. Volume 5 Erwin Schrödinger and the Rise of Wave Mechanics. Part 1 Schrödinger in Vienna and Zurich 1887-1925.'' (Springer, 2001)
*
van der Waerden, B. L., editor, ''Sources of Quantum Mechanics'' (Dover Publications, 1968)
Notes
{{DEFAULTSORT:Honl, Helmut
German quantum physicists
1903 births
1981 deaths
20th-century German physicists
Scientists from Mannheim