rp-Process weak-interaction mediated rates of waiting-point nuclei

TL;DR

This paper calculates electron capture and positron decay rates for specific waiting-point nuclei in stellar environments using the pn-QRPA model, emphasizing the importance of electron capture in rp-process nucleosynthesis.

Contribution

It provides a refined calculation of weak-interaction rates for Kr and Sr nuclei, highlighting the significance of electron capture in rp-process modeling.

Findings

Electron capture and positron decay rates are comparable for certain nuclei.

Electron capture rates on $^{74}$Kr are larger than previous estimates.

Electron capture plays a crucial role in rp-process nucleosynthesis.

Abstract

Electron capture and positron decay rates are calculated for neutron-deficient Kr and Sr waiting point nuclei in stellar matter. The calculation is performed within the framework of pn-QRPA model for rp-process conditions. Fine tuning of particle-particle, particle-hole interaction parameters and a proper choice of the deformation parameter resulted in an accurate reproduction of the measured half-lives. The same model parameters were used to calculate stellar rates. Inclusion of measured Gamow-Teller strength distributions finally led to a reliable calculation of weak rates that reproduced the measured half-lives well under limiting conditions. For the rp-process conditions, electron capture and positron decay rates on $^{72}$Kr and $^{76}$Sr are of comparable magnitude whereas electron capture rates on $^{78}$Sr and $^{74}$Kr are 1--2 orders of magnitude bigger than the corresponding positron decay rates. The pn-QRPA calculated electron capture rates on $^{74}$Kr are bigger than previously calculated. The present calculation strongly suggests that, under rp-process conditions, electron capture rates form an integral part of weak-interaction mediated rates and should not be neglected in nuclear reaction network calculations as done previously.