Adolf Kratzer

B. Adolf Kratzer[1] (October 16, 1893 – July 6, 1983) was a German theoretical physicist who made contributions to atomic physics and molecular physics, and was an authority on molecular band spectroscopy. He was born in Günzburg and died in Münster.

From 1912 to 1914, Kratzer studied physics at the Technische Hochschule München (today, Technische Universität München), and then he spent two years in the army, after which he began studies at the University of Munich under Arnold Sommerfeld. He was granted his doctor of philosophy in 1920; his thesis was on the band spectra of molecules. While at Munich, he was Sommerfeld’s assistant; he had been trained by Sommerfeld’s assistant and student Wilhelm Lenz to fill this role. While at Munich, Kratzer extended the theory of diatomic molecular spectroscopy by including anharmonic forces between the nuclei, which changed the oscillation frequencies. It was Sommerfeld’s practice to send some of his assistants to be personal assistants for physics to the mathematician David Hilbert, at the University of Göttingen.[2] Kratzer was sent to Göttingen during the period 1920 to 1921. Upon his return to Munich, he became a Privatdozent, and it was during this time that he became acquainted with Werner Heisenberg, also a student of Sommerfeld.[3][4][5]

Based on his work at Munich, it was in 1922 that Kratzer's detailed analysis on the cyanide spectroscopic bands was published. His analysis resulted in the introduction of half-integral quantum numbers to account for molecular rotation.[6] During 1922, he was also called as an ordinarius professor of theoretical physics to the University of Münster.[7] Here, Kratzer made contributions to quantum mechanics and became a leading authority in the field of molecular band spectroscopy.[4]

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 as Kratzer, and others, when they were called to other facilities, they effectively became extensions of Sommerfeld’s Institute of Theoretical Physics. This was the case with Kratzer when he went to Münster, as was the case of Sommerfeld’s former student Paul Peter Ewald when he went to the Stuttgart Technische Hochschule.[8]

Kratzer published a number of physics books, based on his lectures on electrodynamics, mechanics, optics, relativity, thermodynamics, and quantum mechanics (wave mechanics). A book on transcendental functions was written with Walter Franz, also a student of Sommerfeld.

The Kratzer potential, a central force in molecular physics, is named in his honor.[9] A potential with the same name has also been used in nuclear physics, as it provides an exact solution of the Bohr hamiltonian.[10]