The addition of a new ($1^{-}$,0) level at 29 MeV excitation energy in ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to the level spectrum of Fiarman and Meyerhof leads to a calculated ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , p)$ to ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , n)$ cross section ratio of 1.67. The calculated ratio falls within the experimental range of 1.6-1.9 without utilizing charge-symmetry violating forces.

NUCLEAR REACTIONS ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , p)$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}(\gamma , n)$. Calculated the ratio of ($\gamma , p$) to ($\gamma , n$) cross sections at the GDR peak to be 1.67.

• Received 17 August 1981

DOI:https://doi.org/10.1103/PhysRevC.27.2417