Analyzing powers for the ${}^9\mathrm{Be}(\overrightarrow{p},\gamma {)}^{10}\mathrm{B}$ reaction were measured by stopping a 100 keV polarized proton beam in a ${}^9\mathrm{Be}$ target. The measured vector analyzing power is $A_y\left(90\mathrm{}°\right)=0.18\mathrm{}\pm 0.03$ for capture to the ground state, with smaller values at $90°$ for the first three excited states. Astrophysical $S$ factors were calculated for each of the final states using a direct capture plus resonance model which fit both the present analyzing power data and the previously reported cross section data. The calculated $S$ factors at $E_p=0\mathrm{}\hspace{0.5em}\mathrm{keV}$ for capture to the ground state and first three excited states were 0.25, 0.34, 0.27, and 0.10 keV b, respectively, which are considerably smaller than previously reported. The observed analyzing powers are explained, within experimental uncertainty, as arising from the interference of the $E1\mathrm{}$ direct capture amplitude with the tails of nearby $p$-wave and $s$-wave resonances.

• Received 13 February 1998

DOI:https://doi.org/10.1103/PhysRevC.58.517