Polarized and unpolarized proton capture on deuterium

Angular distributions of cross section were measured for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}(\mathrm{p}, \gamma ){}_{}{}^3{}_{}{}^{}\mathrm{He}$ reaction at $E_x=9.83, 10.83, 12.78, 15.47, \mathrm{and} 16.12$ MeV and of analyzing power at $E_x=10.83\mathrm{} \mathrm{and} 16.12$ MeV. The data were fitted by expansions of Legendre and, where appropriate, associated Legendre polynomials. The coefficients of those fits are reported. The data at $E_x=10.83\mathrm{} \mathrm{and} 16.12$ MeV were also analyzed under simplifying assumptions to extract the $s=\frac{1}{2}\left(E1\right)$, $s=\frac{1}{2}\left(E2\right)$, and $s=\frac{3}{2}\left(E1\right)$ transition matrix elements, where $s$ represents the incident channel spin. The results indicate that the data are consistent with a 2(3)% $E2\mathrm{}$ and a 3(5)% $s=\frac{3}{2}\left(E1\right)$ admixture at $E_x=10.83\mathrm{}\left(16.12\right)\mathrm{}$ MeV. These results are discussed in light of other recent experiments and calculations.