Neutron capture cross sections in the kev region. Part II. Spin-orbit coupling and the optical model

L. W. Weston*, K. K. Seth, E. G. Bilpuch, H. W. Newson

*Corresponding author for this work

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3 Scopus citations


An intensive study of average neutron capture cross sections of nuclei with 75 ≦ A ≦ 130 has been carried out in the neutron energy region 3 to 200 kev, using the activation method. Assuming s-wave parameters within the limits of error specified by low-energy total cross sections determinations, the data has been analyzed for corresponding p-wave parameters: the neutron strength function Γn(1) D and the γ-ray strength function Γγ D0. It is found that the s- and p-wave γ-ray strength functions are the same within the rather large limits of experimental error for the odd A targets: Rh103, Ag107, Ag109, In115, I127, and As75. The even-even isotopes of Pd, and Mo are more complicated in this respect. The p-wave neutron strength functions Γn(1) D derived from the analysis of these capture cross sections are found to be in agreement with Γn(1) D as obtained from the analysis of neutron total cross sections. These strength functions exhibit a broad, double-peaked, distribution around A = 100 instead of the single peak predicted by the simple optical model. It is shown that the experimental results may be explained by the addition of a small spin-orbit part to the optical potential. The parameters of the square well optical potential V± = V0[1 + iξ + δ 2{-1 ± (2l + 1)}] which are found to fit the p-wave strength functions best are V0 = 41 Mev, ξ = 0.02, δ = 0.085, and R = 1.45 A 1 3 fermis.

Original languageEnglish (US)
Pages (from-to)477-489
Number of pages13
JournalAnnals of Physics
Issue number4
StatePublished - Aug 1960

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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