from studies of X-ray spectra, which could be explained by the Bohr model. Published earlier (1913) in Sitzungsberichten der Kgl. Preuss. Akad. d. Wiss. Described the famous effect of splitting of spectral lines in electric fields (c.f. Zeeman effect) as predicted by Voigt. Observed the same year (1913) as Lo Surdo; the work won a Nobel Physics prize for Stark. Translated in Also in Boorse, H.A., Motz, L. (1966). The world of the atom, edited with commentaries, Basic Books, Inc., New York, pp. 888–901. Formulated the concepts of spontaneous and stimulated emission. Arnold Sommerfeld (1919). See quantum mechanics section. Description on an atomic ionization effect first discovered by Meitner, but named for the later discoverer, Auger. de Broglie, Louis (1924). See quantum mechanics section. Matrix mechanics papers: W. Heisenberg (1925), M. Born and P. Jordan (1925), M. Born, W. Heisenberg, and P. Jordan (1926). See quantum mechanics section. Schroedinger, E (1926). See quantum mechanics section. Relates the experimental discovery of the inelastic scattering of light (predicted theoretically by A. Smekal in 1923) in liquids (with K. S. Krishnan), for which Raman receives the Nobel Prize in Physics in 1930. Observed independently soon after (in crystals) by G. Landsberg and L. I. Mandelstam. Herzberg, Gerhard (1939) Molecular Spectra and Molecular Structure I. Diatomic Molecules Herzberg, Gerhard (1945) Molecular Spectra and Molecular Structure II. Infrared and Raman Spectra of Polyatomic Molecules Herzberg, Gerhard (1966) Molecular Spectra and Molecular Structure III. Electronic Spectra of Polyatomic Molecules This three-volume series is the classic detailed presentation of molecular spectroscopy for physicists and chemists. Herzberg received the 1971 Nobel Prize in Chemistry for his spectroscopic research on the electronic structure and geometry of molecules. Classical mechanics Classical mechanics is the system of physics begun by Isaac Newton and his contemporaries. It is concerned with the motion of macroscopic objects at speeds well below the speed of light. Classic (first and original) English translation: Recent English translation: A three-volume work, often called Principia or Principia Mathematica. One of the most influential scientific books ever published, it contains the statement of Newton's laws of motion forming the foundation of classical mechanics as well as his law of universal gravitation. He derives Kepler's laws for the motion of the planets (which were first obtained empirically). Lagrange's masterpiece on mechanics and hydrodynamics. Based largely on the calculus of variations, this work introduced Lagrangian mechanics including the notion of virtual work,