Gamow–Teller strength distributions of 116Sb and 122Sb using the (3He , t) charge-exchange reaction

The Gamow–Teller strength distributions of 116Sb and 122Sb were measured with the 116,122Sn(3He,t)116,122Sb charge-exchange reactions at 140MeV/u. The measurements were carried out at the Research Center for Nuclear Physics (RCNP) at Osaka University in Osaka, Japan using the Grand Raiden spectrometer. The data were analysed by Multipole-Decomposition Analysis (MDA). The Gamow–Teller strengths summed up to 28MeV are (38 ± 7) % and (48 ± 6) % of the Ikeda sum rule for 116Sb and 122Sb , respectively, if the quasi-free scattering (QFS) contribution is not subtracted. These percentages are (29 ± 7) % and (35 ± 5) % , respectively, if the QFS contribution is maximally subtracted. These results were compared to those from previous measurements of the same isotopes, to recent measurements of 150Pm , and to a Quasi-particle Random-Phase Approximation (QRPA) calculation with Quasi-Particle Vibration Coupling (QPVC). The data suggest that the true QFS contribution is small for 116Sb , but are inconclusive about whether the QFS contribution is small or significant for 122Sb. Therefore, these data may provide an interesting test for the general quenching phenomenon of the Gamow–Teller Resonance (GTR). However, more research to reveal the nature of the QFS contribution is still needed on both the experimental and the theoretical side.