Photon, Atom and Neutron: How Quantum Mechanics Cracked the Nuclear Code

Charles Clark, National Institute of Standards and Technology

Thursday, March 15, 2012
  3:40–4:40 p.m.

At dawn on Thanksgiving Day of 1931, not one person in the world had a clear understanding of the essential facts of nuclear structure.  Deuterium was discovered later that day using elementary quantum mechanics and atomic spectroscopy, and it provided a key clue in solving the puzzle. As we know now, deuterium, the heavy stable isotope of hydrogen, is a bound state of a proton and a neutron.  However, the neutron itself was unknown at the time; it was only discovered around February 17, 1932.  The six months following the discovery of deuterium were among the most productive in the history of science, with many of the most important basic facts of nuclear structure being suddenly assembled then and then rapidly exploited.  Harold Urey was awarded the 1934 Nobel Prize in Chemistry for the discovery of deuterium; eight years later the first nuclear reactor went into operation; the atom bomb was demonstrated three years after that; and the 21st birthday of deuterium was celebrated spectacularly by the detonation of the first hydrogen bomb. We are now in the 80th anniversary of this remarkable period. I will describe how some of the elementary quantum mechanics of atoms and molecules, combined with ingenious experiments, led to these extraordinary discoveries and their applications.  A significant role in these developments was played by Ferdinand G. Brickwedde of the U.S. National Bureau of Standards (now the National Institute of Standards and Technology, or NIST).  Some of Brickwedde's unpublished manuscripts in the collections of the NIST Library add a personal flavor to the public record of events of that time, and enhance appreciation of the roles of different branches of science in the great age of nuclear discovery.  For more information: http://ucrtoday.ucr.edu/3947