Measurement of gamma-emission branching ratios for Gd-154,Gd-156,Gd-158 compound nuclei: Tests of surrogate nuclear reaction approximations for (n,gamma) cross sections

作者：Scielzo N D^*; Escher J E; Allmond J M; Basunia M S; Beausang C W; Bernstein L A; Bleuel D L; Burke J T; Clark R M; Dietrich F S; Fallon P; Gibelin J; Goldblum B L; Lesher S R; McMahan M A; Norman E B; Phair L; Rodriquez Vieitez E; Sheets S A; Thompson I J; Wiedeking M

来源：Physical Review C, 2010, 81(3): 034608.

DOI：10.1103/PhysRevC.81.034608

The surrogate nuclear reaction method can be used to determine neutron-induced reaction cross sections from measured decay properties of a compound nucleus created using a different reaction and calculated formation cross sections. The reliability of (n,gamma) cross sections determined using the Weisskopf-Ewing and ratio approximations are explored for the (155,157)(n,gamma) reactions. Enriched gadolinium targets were bombarded with 22-MeV protons and gamma rays were detected in coincidence with scattered protons using the Silicon Telescope Array for Reaction Studies/Livermore-Berkeley Array for Collaborative Experiments (STARS/LiBerACE) silicon and germanium detector arrays. The gamma-emission probabilities for the Gd-154,Gd-156,Gd-158 compound nuclei were measured at excitation energies up to 12 MeV. It is found that the approximations yield results that deviate from directly measured Gd-155,Gd-157(n,gamma) cross sections at low energies. To extract reliable cross sections, a more sophisticated analysis should be developed that takes into account angular-momentum differences between the neutron-induced and surrogate reactions.

• 出版日期2010-3