John J. Hopfield (spectroscopist)  John Joseph Hopfield (8 August 1891 – 8 January 1953) was a Polish-American spectroscopist, discoverer of the Hopfield bands of oxygen and co-discoverer of the Lyman-Birge-Hopfield bands of nitrogen. Hopfield's major research pursuits included vacuum ultraviolet spectroscopy and solar ultraviolet spectroscopy. He was well known in these disciplines. Hopfield published frequently and produced several patents. Hopfield was born in Poland in 1891. In 1917 he received an A.B. from Syracuse University. From 1918 to 1920 he continued at Syracuse as a Physics Instructor. For the term 1920–1921 Hopfield was awarded a Whiting Research Fellowship. From 1921 to 1923 he was Associate in Physics, then from 1923 to 1925 was Instructor in Physics, and in 1925 appointed to Assistant Professor of Physics at the University of California, Berkeley. Hopfield earned his Ph.D. in Physics, Chemistry in 1923 from the University of California, Berkeley. His advisor was Raymond T. Birge and his thesis subject was: "Spectra of hydrogen, nitrogen, and oxygen in the extreme ultra-violet". At Berkeley, a graduate student working under Hopfield was Gerhard Heinrich Dieke. In 1928 John Joseph Hopfield received a Guggenheim Fellowship appointment: ""for experimental study of the Zeeman effect on the infra-red spectra of oxygen and nitrogen with reference to the classification of the extreme ultra-violet spectra of these elements, chiefly with Professor F. Paschen, of Berlin."" By the time he left Berlin in 1929, the stock market crash and depression had ended most new faculty hiring. Purdue University appointed him as a National Research Council Fellow for two years. He next was employed in creating the physics exhibit for the 1933 ‘Century of Progress’ World’s Fair in Chicago, followed by a position with the Libby-Owens-Ford glass company in Toledo Ohio. With the onset of WWII, physicists were again in great demand, and he moved to Washington DC to participate in war-related research. The end of his career was spent at the Johns Hopkins Applied Physics Laboratory and at the Naval Research Laboratory in the Optics Division in Washington, D.C.. On 8 January 1953, Hopfield died after a brief illness. John J. Hopfield is known and credited for: