Ride the Subways. All will be well...

[NNadir]

We have already seen in section 4.5.2 that the attempt by Bethe and Peierls <495>at developing a simple theory of neutron—proton collision at first appeared to be successful. The formula for the elastic cross section (4.20) derived by these authors provided values in rough agreements with the corresponding experimental results for neutron energies of the order of a few MeV. But when the Columbia University group <596>measured the elastic cross section of slow neutrons against rotons, they found a value more than 14 times larger than the theoretical prediction. The explanation of this serious discrepancy was suggested by Wigner in a private conversation with Bethe who, years later <139> described as follows their conversation: “The discrepancy was explained to me by Wigner in a noisy subway between Columbia University and Penn Station. He said: ‘Well, why do you assume that the singlet state has the same binding energy as the triplet state? Let’s assume a different binding energy and all will be well’.”

This very simple remark was never published by Wigner. It was reported in the article by Bethe and Bacher “in the Reviews of Modern Physics <108>... Our paper was published in 1936. Having the singlet state of the deuteron higher than the triplet state, of course, would reintroduced a little bit of Heisenberg forces”.

This comes from a very interesting account by http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TVP-46WX8X2-14&_user=1082852&_coverDate=09%2F30%2F1984&_alid=844526030&_rdoc=21&_fmt=high&_orig=search&_cdi=5540&_sort=d&_docanchor=&view=c&_ct=39&_acct=C000051401&_version=1&_urlVersion=0&_userid=1082852&md5=16f39ba653876704fc170f51e2f99452">From the discovery of the neutron to the discovery of nuclear fission

Wigner and Breit played an important role in the development of fission physics by introducing the Breit-Wigner systematics for neutron resonances.

A fun and cool read, if you're into that sort of thing.

[patrice]

1. I'll share it with someone who is. Thanks! nt

[NNadir]

2. My pleasure.