Measurement of theHe4(γ,n)reaction from23<Eγ<70MeV

A comprehensive set of $^{4}\mathrm{He}$$(\ensuremath{\gamma},n)$ absolute cross-section measurements was performed at MAX-lab in Lund, Sweden. Tagged photons from $23l{E}_{\ensuremath{\gamma}}l70$ MeV were directed toward a liquid $^{4}\mathrm{He}$ target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for 14 photon energies. The results have been subjected to complementary transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as recoil-corrected continuum shell-model, resonating group method, and effective interaction hyperspherical-harmonic expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983.