The ${\mathrm{He}}^3(\gamma ,d)p$ differential cross section at 90° in the laboratory system has been measured in the gamma-ray energy range of 8.5 to 46 MeV. A broad peak with a maximum of 93 μb/sr at 11 MeV is observed. A theory of Gunn and Irving (for a radius parameter of 2.7 F) gives a good fit to the measured cross section. When compared with other experiments, the present data agree well with the 90° data of Berman et al. and Finckh et al. Taking into account angular-distribution corrections, they agree within statistics with the total cross section of Gorbunov et al. The ${\mathrm{He}}^3(\gamma ,2p)n$ proton energy spectrum produced by 40-MeV bremsstrahlung has also been measured. This spectrum is found to disagree in magnitude with predictions from theories by Gunn and Irving, and by Delves. The spectrum agrees fairly well with that expected from the ${\mathrm{He}}^3(\gamma ,2p)n$ cross section measured by Gorbunov et al. A survey of sum-rule predictions is also included.

• Received 7 December 1964

DOI:https://doi.org/10.1103/PhysRev.138.B372