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

Half-lives and energies of γ rays emitted in the decay of isomeric states of nuclei in the vicinity of the doubly magic ¹⁰⁰Sn were measured in a decay spectroscopy experiment at Rikagaku Kenkyusho (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 E 2 γ ray from a new (4⁺) isomer with T_{1 /2}=0.23 (6 ) μ s in ⁹²Rh, a 44-keV E 2 γ ray from the (15⁺) isomer in ⁹⁶Ag, and T_{1 /2}(6⁺) =13 (2 ) ns in ⁹⁸Cd. 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 γ rays in ¹⁰⁰Sn, new constraints on the T_{1 /2}, γ -ray energy, and internal conversion coefficients are proposed for the hypothetical isomer in ¹⁰⁰Sn.