Calculations for ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{p}){}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{n}){}_{}{}^3{}_{}{}^{}\mathrm{He}$ have been performed with the recoil-corrected continuum shell model. A charge-symmetry breaking interaction has been introduced in an effort to explain the large value (∼2) observed in recent experiments for the cross section ratio $R=\frac{\sigma (\gamma , \mathrm{p})}{\sigma (\gamma , \mathrm{n})}$. The calculations indicate that it is highly unlikely that such a large value of the cross section ratio can be obtained within standard theoretical assumptions.

NUCLEAR REACTIONS ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , \mathrm{p})$, ($\gamma , \mathrm{n}$), $E_x=20-36\mathrm{}$ MeV; calculated $\sigma \mathrm{}\left(E\right)\mathrm{}$, expansion coefficients $a_k\mathrm{}\left(E\right)\mathrm{}$, $B_k\mathrm{}\left(E\right)\mathrm{}$ for $\sigma (E, \theta )$, $P(E, \theta )$. ${}_{}{}^3{}_{}{}^{}\mathrm{H}$(p,n); calculated $A\mathrm{}\left(E\right)\mathrm{}$, $P\left(E\right)\mathrm{}$. Studied influence of charge symmetry breaking interaction.

• Received 22 February 1983

DOI:https://doi.org/10.1103/PhysRevC.28.1000