Band structure and hole-core coupling in 111In

Abstract

The level structure of 111 In was studied using the 109Ag(α, 2nγ) 111 In reaction. The experiments included γ-ray excitation function, γ-γ coincidence, γ-ray angular distribution and conversion electron measurements. The structure of the cascade of positive-parity states with spins in the range from 9 2 + to 17 2 + is well described by coupling a g 9 2 proton-hole to the quadrupole vibrations of th 112Sn core. Branching and mixing ratios of γ-rays decaying within this band are reproduced satisfactorily by hole-phonon coupling calculations. A calculation of the leading order contributions in the transitional matrix elements shows that in particle-phonon coupling the sign of the mixing ratios is related to the sign of the quadrupole moment of the band head. This is in agreement with the experimental results. The half-life of the isomeric state at 2717 keV (J π = 21 2 +, T 1 2 = 13.8 ns) is related to the half-life of the 6 + isomer in the adjacent 112Sn nucleus. Also the negative-parity states can be interpreted within the hole-core coupling model. No evidence was found for bands based on deformed proton states.