Properties of gamma-decaying isomers and isomeric ratios in the Sn-100 region

Abstract

Half-lives and energies of gamma rays emitted in the decay of isomeric states of nuclei in the vicinity of the doubly magic Sn-100 weremeasured in a decay spectroscopy experiment at RikagakuKenkyusho (The Institute of Physical and Chemical Research) of Japan Nishina Center. The measured half-lives, some with improved precision, are consistent with literature values. Three new results include a 55-keV E2 gamma ray from a new (4(+)) isomer with T-1/2 = 0.23(6) mu s in Rh-92, a 44-keV E2 gamma ray from the (15(+)) isomer in Ag-96, and T-1/2(6(+)) = 13(2) ns in Cd-98. Shell-model calculations of electromagnetic transition strengths in the (p(1/2), g(9/2)) model space agree with the experimental results. In addition, experimental isomeric ratios were compared to the theoretical predictions derived with an abrasion-ablation model and the sharp cutoff model. The results agreed within a factor of 2 for most isomers. From the nonobservation of time-delayed gamma rays in Sn-100, new constraints on the T-1/2, gamma-ray energy, and internal conversion coefficients are proposed for the hypothetical isomer in Sn-100.