The single-particle character of states outside the doubly magic (radioactive) nucleus ${}^{56}\mathrm{Ni}$ has been determined through a measurement of the $(d,p)$ neutron transfer reaction using inverse kinematics. From the spectroscopic factors of the low-lying states in ${}^{57}\mathrm{Ni}$, the astrophysically interesting yield for the ${}^{56}\mathrm{Ni}(p,\gamma )$ reaction to the mirror nucleus ${}^{57}\mathrm{Cu}$ has been calculated, utilizing charge symmetry. The rate for this reaction in the temperature range typical of novae, supernovae, and x-ray bursts is found to be more than 10 times higher than previously assumed.

• Received 29 August 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.676