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

The EC/β⁺ decay of ¹⁰⁵Sn was reinvestigated by using ⁵⁸Ni(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.