E2Isovector Giant Resonance as Seen through the Capture of Fast Neutrons

The forward-to-backward asymmetry of high-energy photons emitted in the radiative capture of neutrons with energies up to 20 MeV was measured for ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The asymmetry increases abruptly from small values to large ones near $E_{\gamma }\sim 23$ MeV supporting the location in that neighborhood of the $E2\mathrm{}$ giant isovector resonance.