Study of the energy levels of ⁷⁴ Ge using nuclear photoexcitation

Elastic and inelastic scattering of monochromatic photons were used for studying the energy levels of ⁷⁴Ge; the photons were produced by thermal-neutron capture in iron. The energy of the resonance level was found to be 6.018 MeV. Assuming the high-energy lines to be primary transitions deexciting the resonance level, eight energy levels were found from the ground state up to 3 MeV, four of which are believed to be new levels in ⁷⁴Ge. The angular distribution of the elastic and inelastic lines were measured and the following spin-parity determinations were made: 0.596(2+), 1.206(2⁺), 1.486(0⁺), 2.200(2⁺), 2.229(0⁺), and 6.018(1^-). The parities of the first and last levels were directly determined by polarization measurements using a Compton polarimeter. The parities of the other levels were inferred from the radiation strengths of the corresponding high-energy transitions. The total and partial radiative widths of the 6.018-MeV level were also measured. The M2/E1 mixing ratios for the high-energy transitions were obtained. For one transition, this ratio was x²=0.017, which is much higher than that predicted by the simple theory.