Helmut Hönl
Encyclopedia
Helmut Hönl was a German theoretical physicist who made contributions to quantum mechanics
and the understanding of atomic and molecular structure.
From 1921 to circa 1923, Hönl studied at the University of Heidelberg and the University of Göttingen, followed by the University of Munich, where he studied under Arnold Sommerfeld
. 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
. 1940 he became extaordinary professor at the University of Erlangen and 1943 ordinary professor for theoretical physics at the University of Freiburg, where he emerited 1971.
Even before acquiring his doctorate at Munich
, Hönl had done seminal work 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
. As is the case in any fast developing field with a high level of interest, others independently make similar findings. This was the case with his work on the intensity of Zeeman effect
spectral lines. Both Hönl and Samuel Goudsmit 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
formulation of quantum theory in 1925, Werner Heisenberg
, a former student of Sommerfeld, working with Max Born
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
, especially the Sommerfeld-Bohr model
: the Theoretical Physics Institute at the University of Munich, under Arnold Sommerfeld
, the Institute of Theoretical Physics at the University of Göttingen, under Max Born
, and the Institute of Theoretical Physics, under Niels Bohr
. 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
to work with Paul Peter Ewald
, who received his Ph.D. under Sommerfeld and became ordinarius professor of theoretical physics at Stuttgart Technische Hochschule in 1921. At Stuttgart, Ewald and Hönl worked on the quantum theory atomic and molecular structure and solid-state physics
. 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).
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
and the understanding of atomic and molecular structure.
From 1921 to circa 1923, Hönl studied at the University of Heidelberg and the University of Göttingen, followed by the University of Munich, where he studied under Arnold Sommerfeld
Arnold Sommerfeld
Arnold Johannes Wilhelm Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics...
. He was granted his doctor of philosophy in 1926. In 1929, he became assistant to Paul Peter Ewald
Paul Peter Ewald
Paul Peter Ewald was a German-born U.S. crystallographer and physicist, a pioneer of X-ray diffraction methods.-Education:...
at the Stuttgart
Stuttgart
Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....
Technische Hochschule
Technische Hochschule
Technische Hochschule is what an Institute of Technology used to be called in German-speaking countries, as well as in the Netherlands, before most of them changed their name to Technische Universität or Technische Universiteit in the 1970s and in the...
until 1933, after which he was a Privatdozent
Privatdozent
Privatdozent or Private lecturer is a title conferred in some European university systems, especially in German-speaking countries, for someone who pursues an academic career and holds all formal qualifications to become a tenured university professor...
. 1940 he became extaordinary professor at the University of Erlangen and 1943 ordinary professor for theoretical physics at the University of Freiburg, where he emerited 1971.
Even before acquiring his doctorate at Munich
Munich
Munich The city's motto is "" . Before 2006, it was "Weltstadt mit Herz" . Its native name, , is derived from the Old High German Munichen, meaning "by the monks' place". The city's name derives from the monks of the Benedictine order who founded the city; hence the monk depicted on the city's coat...
, Hönl had done seminal work which contributed to the advancement of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
and the understanding of atomic and molecular structure and spectra. Some of his work was done in collaboration with Fritz London
Fritz London
Fritz Wolfgang London was a German theoretical physicist. His fundamental contributions to the theories of chemical bonding and of intermolecular forces are today considered classic and are discussed in standard textbooks of physical chemistry.With his brother Heinz, he made a significant...
. As is the case in any fast developing field with a high level of interest, others independently make similar findings. This was the case with his work on the intensity of Zeeman effect
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 analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field...
spectral lines. Both Hönl and Samuel Goudsmit and Ralph de Laer Kronig
Ralph Kronig
Ralph Kronig was a German-American physicist . He is noted for the discovery of particle spin and for his theory of x-ray absorption spectroscopy...
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
Matrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925.Matrix mechanics was the first conceptually autonomous and logically consistent formulation of quantum mechanics. It extended the Bohr Model by describing how the quantum jumps...
formulation of quantum theory in 1925, Werner 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...
, a former student of Sommerfeld, working with 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...
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
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...
and the interpretation of atomic and molecular structure, based on atomic and molecular 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...
, especially the Sommerfeld-Bohr model
Bohr model
In atomic physics, the Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction,...
: the Theoretical Physics Institute at the University of Munich, under Arnold Sommerfeld
Arnold Sommerfeld
Arnold Johannes Wilhelm Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics...
, the Institute of Theoretical Physics at the University of Göttingen, under 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 the Institute of Theoretical Physics, under 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...
. 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
Stuttgart
Stuttgart is the capital of the state of Baden-Württemberg in southern Germany. The sixth-largest city in Germany, Stuttgart has a population of 600,038 while the metropolitan area has a population of 5.3 million ....
Technische Hochschule
Technische Hochschule
Technische Hochschule is what an Institute of Technology used to be called in German-speaking countries, as well as in the Netherlands, before most of them changed their name to Technische Universität or Technische Universiteit in the 1970s and in the...
to work with Paul Peter Ewald
Paul Peter Ewald
Paul Peter Ewald was a German-born U.S. crystallographer and physicist, a pioneer of X-ray diffraction methods.-Education:...
, who received his Ph.D. under Sommerfeld and became ordinarius professor of theoretical physics at Stuttgart Technische Hochschule in 1921. At Stuttgart, Ewald and Hönl worked on the quantum theory atomic and molecular structure and solid-state physics
Solid-state physics
Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from...
. 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).
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 in 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)