Czerny attracted attention at the time when, following the Stern-Gerlach experiment (1922), which demonstrated the existence of half-integer quantum numbers in electron spin, he also found them in the rotation bands of molecules (gaseous hydrogen halides).
His subsequent study of the rotation bands on alkali halide crystals (with R. Bowling Barnes, C. H. Cartwright) provided the first evidence of what were later described as multiphonon effects.
In 1927 he earned his habilitation and in 1934 he became an associate professor in Berlin (as the successor Peter Pringsheim, who was dismissed by the Nazi regime), but left after the institute in Berlin was switched to military research due to the change in leadership from Walther Nernst to Erich Schumann and the scientific environment deteriorated due to confidentiality regulations.
His predecessor Karl Wilhelm Meissner, who wanted to bring Czerny to Frankfurt in 1934, had previously been dismissed there by the National Socialists.
[1] In 1972 he published a paper on changes in the optics and vision of the eye after cataract surgery (e.g. greater sensitivity in the ultraviolet).