The Gamow-Teller decay of 105Sn to three-particle states in 105In

Abstract

The EC/ β + decay of 105Sn was reinvestigated by using 58 Ni(5 MeV/u) + 50Cr reactions, chemically selective on-line mass separation and γ-ray spectroscopy. The half-life of 105Sn has been determined as 34 ± 1 s. Out of 104 γ transitions ascribed to the 105Sn decay, 89 have been placed in the decay scheme including 52 excited states of 105In. From the EC/ β + feeding of individual states, the distribution of the Gamow-Teller (GT) strength has been derived. It is shown that the main part of the GT strength is associated with the feeding of 105In levels having excitation energies above 3 MeV. This observation can be interpreted as a sign of dominant feeding of three-quasiparticle states in 105In, which correspond to the π( g 9 2 ) −1νg 7 2 νd 5 2 shell-model configuration spread over many levels. The sum of the GT strength deduced from the present gamma-ray data of B Σ (GT) = 1.46 provides a lower limit to the total GT strength. Many weak transitions, mainly from high-energy levels, may not have been detected in this study and therefore part of the strength may be missed. An indirect support for this conclusion has been obtained from the analysis of the indium KX-rays intensity. This analysis indicates about 50% contribution of the electron-capture to the beta decay of 105Sn, which is interpreted as a sign of a predominant feeding of the high-energy 105In states with B Σ (GT) ⩾ 3. The observed GT distribution and strength will be compared to results obtained from a finite-Fermi-system theory and a large-basis shell-model calculation. The core-polarization and higher-order hindrance factors will be discussed.