Nuclear structure properties and stellar weak rates for Se-76: Unblocking of the Gamow Teller strength

Abstract

At finite temperatures (>= 10(7)K), Se-76 is abundant in the core of massive stars and electron capture on Se-76 has a consequential role to play in the dynamics of core-collapse. The present work may be classified into two main categories. In the first phase we study the nuclear structure properties of Se-76 using the interacting boson model-1 (IBM-1). The IBM-1 investigations include the energy levels, B (E2) values and the prediction of the geometry. We performed the extended consistent-Q formalism (ECQF) calculation and later the triaxial formalism calculation (constructed by adding the cubic term to the ECQF). The geometry of Se-76 can be envisioned within the formalism of the potential energy surface based on the classical limit of IBM-1 model. In the second phase, we reconfirm the unblocking of the Gamow Teller (GT) strength in Se-76 (a test case for nuclei having N > 40 and Z < 40). Using the deformed pn-QRPA model we calculate GT transitions, stellar electron capture cross section (within the limit of low momentum transfer) and stellar weak rates for Se-76. The distinguishing feature of our calculation is a state-by-state evaluation of stellar weak rates in a fully microscopic fashion. Results are compared with experimental data and previous calculations. The calculated GT distribution fulfills the Ikeda sum rule. Rates for, beta-delayed neutrons and emission probabilities are also calculated. Our study suggests that at high stellar temperatures and low densities, the beta(+)-decay on Se-76 should not be neglected and needs to be taken into consideration along with electron capture rates for simulation of presupernova evolution of massive stars. (C) 2017 Elsevier B.V. All rights reserved.