Light, Atoms and Nuclei: The Optical Discovery of Deuterium

Charles W. Clark and Joseph Reader

Eighty years have passed since atomic spectroscopy was used to discover deuterium, or “heavy hydrogen.” The element has played a transformational role in the development of nuclear energy and isotope chemistry. Currently, it is helping astronomers to understand the very origins of our universe.


feature2-img1.jpgImage of glowing deuterium in an inertial electroconfinement reactor. The pinkish-red glow is due to the Balmer lines that provided the basis for Bohr’s theory of the atom.


At dawn on Thanksgiving Day, 1931, no one in the world had an accurate idea of the nature of the atomic nucleus. That day, at Columbia University in New York, Harold C. Urey and George M. Murphy measured the optical emission spectra of samples of hydrogen gas received by railway express shipment from the National Bureau of Standards in Washington, D.C., U.S.A. Urey arrived home late for Thanksgiving dinner, but with the news that he had discovered the mass 2 isotope of hydrogen. He later remarked, “I thought maybe my discovery might have the practical value of, say, neon in neon signs. My colleagues felt I was exaggerating [its] importance.”

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