Angular-Correlation Studies of the ReactionsC12(He3,α)C11andO16(He3,α)O15

Abstract

The 4.32- and 4.81-MeV levels of ${\mathrm{C}}^{11}$ and the 6.79- and 6.86-MeV levels of ${\mathrm{O}}^{15}$, have been studied using the particle-gamma angular-correlation method of Litherland and Ferguson. The spin of the ${\mathrm{C}}^{11}$ 4.32-MeV level has been established as $\frac{5}{2}$ and the mixing ratio for the transition 4.32 → 0 has been measured: $\delta =+\left({{0.16}_{-0.02\mathrm{}}}^{+0.05\mathrm{}}\right)$. A probable spin assignment $J=\frac{3}{2}$ has been determined for the ${\mathrm{C}}^{11}$ 4.81-MeV level. For this assignment, the mixing ratios of the 4.81 → 2.0 and 4.81 → 0 transitions have been obtained: $\delta =-(0.30\mathrm{}\pm 0.6)$ and $\delta =\left({{0.0}_{-0.09\mathrm{}}}^{+0.01\mathrm{}}\right)$, respectively. A spin assignment of $J=\frac{3}{2}$ has been confirmed for the ${\mathrm{O}}^{15}$ 6.79-MeV level. The ${\mathrm{O}}^{15}$ 6.86-MeV level has probably a spin $J=\frac{5}{2}$, but $J=\frac{3}{2}$ cannot be eliminated. The mixing ratios for the 6.86 → 5.24 ($\frac{5}{2}\to \frac{5}{2}$) and the 5.24 → 0 ($\frac{5}{2}\to \frac{1}{2}$) transitions were found to be $\delta =+\left({{0.05}_{-0.10\mathrm{}}}^{+0.07\mathrm{}}\right)$ and $\delta =\left({{0.0}_{-0.05\mathrm{}}}^{+0.12\mathrm{}}\right)$ or +($2.9_{-0.9\mathrm{}}^{}{}_{}{}^{+1.8\mathrm{}}$), respectively. The results are compared to previous experiments and theoretical predictions.