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Working on a theory of deutron disintegration

RELATED STORIES

Chadwick and Goldhaber's work on deuteron disintegration
Hans Bethe Scientist
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Peierls found out that a very interesting experiment was being done at Cambridge by Chadwick and Goldhaber. Goldhaber later became the Director of the Brookhaven National Laboratory. He was a very smart graduate student at that time, and they had discovered that the deuteron, that is the atom of hydrogen of atomic weight 2, could be disintegrated by gamma rays from a natural radioactive substance. You have to remember that at that time there was not yet available any accelerated proton which had high energy, so one had to rely on the high energy particles which nature provided, and fortunately the gamma ray from one of the thorium daughters has an energy just big enough to disintegrate a deuteron, in fact an energy of 2.6 million electron volts, and the binding energy of the deuteron is 2.2. So they managed to disintegrate the deuteron and get the track of the proton which comes out of it to measure the length of that track, and then using the range-energy relation they could determine that the proton which came out had an energy of about 0.2 million electron volts. Neutron obviously had the same energy, so they could calculate the deuteron binding energy.

The late German-American physicist Hans Bethe once described himself as the H-bomb's midwife. He left Nazi Germany in 1933, after which he helped develop the first atomic bomb, won the Nobel Prize in Physics in 1967 for his contribution to the theory of nuclear reactions, advocated tighter controls over nuclear weapons and campaigned vigorously for the peaceful use of nuclear energy.

Listeners: Sam Schweber

Silvan Sam Schweber is the Koret Professor of the History of Ideas and Professor of Physics at Brandeis University, and a Faculty Associate in the Department of the History of Science at Harvard University. He is the author of a history of the development of quantum electro mechanics, "QED and the men who made it", and has recently completed a biography of Hans Bethe and the history of nuclear weapons development, "In the Shadow of the Bomb: Oppenheimer, Bethe, and the Moral Responsibility of the Scientist" (Princeton University Press, 2000).

Tags: Brookhaven National Laboratory, Rudi Peierls, James Chadwick, Gerson Goldhaber

Duration: 2 minutes, 2 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008