# Single-particle shell strengths near the doubly magic nucleus $^{56}$Ni and the $^{56}$Ni(p,$\gamma$)$^{57}$Cu reaction rate in explosive astrophysical burning

## TL;DR

This study measures the single-particle strengths near $^{56}$Ni and refines the $^{56}$Ni(p,$ extgamma$)$^{57}$Cu reaction rate, crucial for understanding nucleosynthesis in explosive astrophysical environments like x-ray bursts.

## Contribution

It provides new experimental data on nuclear structure and reaction rates near $^{56}$Ni, improving models of astrophysical nucleosynthesis.

## Key findings

- Determined spectroscopic factors for $^{57}$Cu-$^{57}$Ni$ states.
- Compared experimental results with shell-model calculations.
- Refined the $^{56}$Ni(p,$ extgamma$)$^{57}$Cu reaction rate.

## Abstract

Angle-integrated cross-section measurements of the $^{56}$Ni(d,n) and (d,p) stripping reactions have been performed to determine the single-particle strengths of low-lying excited states in the mirror nuclei pair $^{57}$Cu-$^{57}$Ni situated adjacent to the doubly magic nucleus $^{56}$Ni. The reactions were studied in inverse kinematics utilizing a beam of radioactive $^{56}$Ni ions in conjunction with the GRETINA $\gamma$-array. Spectroscopic factors are compared with new shell-model calculations using a full $pf$ model space with the GPFX1A Hamiltonian for the isospin-conserving strong interaction plus Coulomb and charge-dependent Hamiltonians. These results were used to set new constraints on the $^{56}$Ni(p,$\gamma$)$^{57}$Cu reaction rate for explosive burning conditions in x-ray bursts, where $^{56}$Ni represents a key waiting point in the astrophysical rp-process.