Inelastic Scattering of Monochromatic Photons from the 7.64-MeV Level ofNi62

Abstract

The nuclear resonant scattering of the monochromatic iron capture gamma rays from natural nickel was studied with a single NaI crystal and a three-crystal pair spectrometer. The spectrum of the scattered photons exhibits three photon groups of 7.64, 6.47, and 5.38 MeV with relative intensities 0.69, 0.08, and 0.23, respectively. The spectrum of the low-energy cascade photons in coincidence with the scattered photons identifies these groups with the transitions from the 7.64-MeV resonant level to the ${0}^{+}$ ground state and the first (${2}^{+}$, 1.17 MeV) and second (${0}^{+}$, 2.05 MeV) vibrational levels in ${\mathrm{Ni}}^{62}$. Angular distribution measurements of the elastically scattered photons show that the 7.64-MeV level in ${\mathrm{Ni}}^{62}$ has angular momentum 1. The elastic-scattering cross section averaged over the incident gamma rays was determined to be $〈{\ensuremath{\sigma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}〉=190\ifmmode\pm\else\textpm\fi{}40$ mb.