Polarized protons were used to measure the analyzing power of $\mathrm{the}{}^9\mathrm{Be}(\overrightarrow{p},\gamma {)}^{10}\mathrm{B}$ reaction for $E_p=280\mathrm{}–0\hspace{0.5em}\mathrm{keV}.$ The analyzing power for the ground state transition compared to calculations leads to a spin-parity assignment of $2^{+}$ for the 7.478 MeV state of ${}^{10}\mathrm{B}.$ This $2^{+}$ assignment is consistent with other observables for this reaction and is predicted by cluster and shell model calculations. It is found that the $2^{+}$ assignment leads to a value for the astrophysical S factor for capture to the ground state of ${}^{10}\mathrm{B}$ of $S\left(0\right)=0.20\mathrm{}\hspace{0.5em}\mathrm{keV}\mathrm{}\mathrm{b}$ which is about 40% smaller than that obtained with a $2^{-}$ assignment.

• Received 12 October 1998

DOI:https://doi.org/10.1103/PhysRevC.59.3425