Spectroscopy and the quantum revolution: Old quantum theory gives way to quantum mechanics

HIST 15

Kenneth R. Metz, kenneth.metz.1@bc.edu, Department of Chemistry, Boston College, 2609 Beacon Street, Chestnut Hill, MA 02467
Most chemists are aware of the dynamic historical interplay between the evolution of spectroscopic theory and the development of quantum theory in the early part of the twentieth century. Beginning with Bohr's 1913 planetary model of the atom, spectra provided the ultimate proving ground for new ideas in quantum theory, culminating in the matrix / wave mechanics revolution of the mid-1920's. Two pivotal monographs provide snapshots of the state of theoretical development in spectroscopy as old quantum theory evolved into quantum mechanics. The first is Arnold Sommerfeld's 1919 Atombau und Spektrallinien (English edition, 1923), a masterful exposition of the modified Bohr model, or old quantum theory, at its zenith. The second is that of Ruark and Urey (Atoms, Molecules and Quanta, 1930), which incorporated results from the new wave mechanics and signaled the arrival of an enormously successful era in spectroscopy. This presentation will compare and contrast these treatments.