Raymond Thayer Birge (13.03.1887-22.03.1980) was an American physicist and a member of the National Academy of Sciences (1932). He was born in Brooklyn. He graduated from the University of Wisconsin (1909). In 1913-18 he worked at Syracuse University and in 1918-55 at the University of California (professor from 1933).
His research concerned the quantum theory of molecular spectra, spectroscopy, statistics, the refinement and analysis of the physical constants, and the history of physics. In 1926 he developed a method of determining the heat of dissociation of diatomic molecules. He discovered (1929) the isotope carbon-13 and predicted (1931) the existence of deuterium. In the years that followed he worked on refining the values of the physical constants; in particular, he carried out the first complete critical analysis and calculation of the physical constants by the method of least squares. In 1941 he determined the speed of light with high accuracy.
In 1955 he was president of the American Physical Society.