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Binding of nuclear matter: simultaneous exchange of two pions


Experimental research on the binding of nuclear matter
Hans Bethe Scientist
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When we tried to calculate the binding energy of 16MeV, we failed. We had two choices: we could give the right binding energy, but then the nuclear density would be twice as high as is actually observed; or we could get the right density and then the binding energy would be much too high. The solution of that was found by a postdoctoral fellow of mine, Panderia Pandi who has stayed with this subject ever since and is a professor at the University of Illinois in Urbana. He has done the most elaborate calculations using of course modern day computers to the fullest. He works together with the Argonne National Laboratory and two of his former students are there as staff members, and they have found that you better start from light nuclei, namely start from nuclei containing three nucleons. Two nucleons is obvious - I did that with Peierls back in 1934 - but three nucleons is a real problem. And so this group found that there is a force between three nucleons where you have a meson exchange between number one and two, then two and three, and then back from three to one. And from the behavior of the nucleus Hydrogen 3 and Helium 3, they could deduce the strength of this force, and they could then prove that helium 4 could be satisfactorily explained with just the three body force, you didn't need to go to four body [forces]. Well, a three body force gives about 1 MeV of the 16, and it gives the right density, and so you now can get the right density together with the right binding energy. But my initial plan to put it all in terms of the two nucleon interaction did not work out, and... but it stimulated a whole development of further calculations. I was busy with that for many years from '55 to about '68.

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: University of Illinois, Argonne National Laboratory

Duration: 3 minutes, 11 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008