Astrophysical Implication of Low E(2^+_1) in Neutron-rich Sn Isotopes

TL;DR

This paper investigates the impact of low E(2+_1) states in neutron-rich Sn isotopes on nuclear astrophysics, focusing on beta-decay rates and their implications for r-process nucleosynthesis.

Contribution

It provides theoretical calculations of beta-decay rates of exotic Sn isotopes using shell model, highlighting their temperature dependence and astrophysical significance.

Findings

Decay rates decrease with temperature due to excited state populations.

Increased half-life of 136Sn may significantly affect r-process nucleosynthesis.

Shell model calculations of B(GT) values support the decay rate analysis.

Abstract

The observation and prediction of unusually depressed first excited 2^+_1 states in even-A neutron - rich isotopes of semi-magic Sn above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general. In the present work, the beta-decay rates of the exotic even Sn isotopes (134,136Sn) above the 132Sn core have been calculated as a function of temperature (T). In order to get the necessary ft values, B(GT) values corresponding to allowed Gamow Teller (GT-) beta-decay have been theoretically calculated using shell model. The total decay rate shows decrease with increasing temperature as the ground state population is depleted and population of excited states with slower decay rates increases. The abundance at each Z value is inversely proportional to the decay constant of the waiting point nucleus for that particular Z. So the increase in half-life of isotopes of Sn, like 136Sn, might have substantial impact on the r-process nucleosynthesis.