Evaluation of the ${}^{35}$K($p$,${\hat{I}}^3$)${}^{36}$Ca reaction rate using the ${}^{37}$Ca($p$,$d$)${}^{36}$Ca transfer reaction

Abstract

A recent sensitivity study has shown that the ${}^{35}$K$(p,{\hat{I}}^3{)}^{36}$Ca reaction is one of the ten $(p,{\hat{I}}^3)$ reaction rates that could significantly impact the shape of the calculated X-ray burst light curve. In this work, we propose to reinvestigate the ${}^{35}$K$(p,{\hat{I}}^3{)}^{36}$Ca reaction rate, as well as related uncertainties, by determining the energies and decay branching ratios of ${}^{36}$Ca levels, within the Gamow window, in the 0.5 to 2 GK X-ray burst temperature range. These properties were studied using the one neutron pick-up transfer reaction ${}^{37}$Ca$(p,d{)}^{36}$Ca in inverse kinematics using a radioactive beam of ${}^{37}$Ca at 48 MeV nucleon${}^{-1}$. The experiment performed at GANIL, used the liquid Hydrogen target CRYPTA, the MUST2 detector array for the detection of the light charged particles and a zero degree detection system for the outgoing heavy ions. The atomic mass of ${}^{36}$Ca is confirmed and new resonances have been proposed together with their proton decay branching ratios. This spectroscopic information, used in combination with recent theoretical predictions for the ${\hat{I}}^3$-width, were used to calculate the ${}^{35}$K$(p,{\hat{I}}^3{)}^{36}$Ca reaction rate. The recommended rate of the present work was obtain within a uncertainty factor of 2 at 1 sigma. This is consistent, with the previous estimate in the X-ray burst temperature range. A large increase of the reaction rate was found at higher temperatures due to two newly discovered resonances. The ${}^{35}$K$(p,{\hat{I}}^3{)}^{36}$Ca thermonuclear reaction rate is now well constrained by the present work in a broad range of temperatures. Our results show that the ${}^{35}$K$(p,{\hat{I}}^3{)}^{36}$Ca reaction does not affect the shape of the X-ray burst light curve, and that it can be removed from the list of the few influential proton radiative captures reactions having a strong impact on the light curve.

Published 13 May 2021 in PRC