Decay spectroscopy of 117,118Sn

Abstract

The low-lying states of 117,118Sn have been studied from the decay of 117g,118mSb, and 117mSn. These long-lived species were populated through the reaction 4He + natIn at Elab = 32 MeV. Singles, as well as γ-γ coincidence data, were acquired. The uncertainties in the placement of some of the γ-rays in the excitation spectra of 118Sn observed by previous workers have been removed. A γ-ray (984 keV) previously assigned to 118Sn has been eliminated from the level scheme, based on the present analysis. The decay half-lives of 117g,118mSb have been remeasured. The slope method and deconvolution technique have been used to determine the half-lives of a few isomeric states in 117,118Sn. The results are interpreted in the framework of large scale shell model calculations performed in the 50 - 82 valence shell using truncations. Although the excitation energies were not reproduced well, the theoretical calculations could reasonably reproduce the isomers' transition probabilities due to their nearly pure configuration.