Neutron Capture in Tin Isotopes at Stellar Temperatures

THEORIES of stellar nucleosynthesis have emphasized the importance of neutron capture ( s - and r -processes occurring in giant stars and supernovæ respectively) in producing the heavy elements 1,2 . For the s -process, cosmic isotopic abundances are predicted to show an inverse proportionality to the neutron capture cross-sections. While some nuclei can be produced by only one process or the other, the abundances can be most accurately measured for isotopes of a single element. Thus the many isotopes of tin provide the best opportunity to test the theories and to determine such parameters as the relative contribution of supernovæ to the material of the solar system. Tin-116 cannot be formed by the r -process, whereas tin-122 and tin-124 can only be so formed. In addition, the r -process is expected to be only a minor contributor 2 to the production of tin-117, -118, -119, and -120.