J. Goto

Medium-spin states in {sup 70}Ge and the role of the g{sub 9/2} orbital

Medium-spin states of {sup 70}Ge have been studied via the {sup 60}Ni({sup 12}C,2p{gamma}){sup 70}Ge reaction at 45 MeV. The ground-state band and the second 0{sup +} band have been extended to the 12{sup +} and 8{sup +} states, respectively. Two negative-parity bands, one of which has a coupled structure and the other has a decoupled structure, have been observed additionally. Although the latter decoupled structure was known up to the (21{sup -}) state from a previous experiment, the part of the level scheme up to the 15{sup -} state has been largely modified by the present experiment. Backbendings observed in the positive- and negative-parity yrast bands have been compared with those of the neighboring even Ge isotopes. The experimental level structure has been compared with the shell-model calculations in the model space (2p{sub 3/2}, 1f{sub 5/2}, 2p{sub 1/2}, 1g{sub 9/2}) employing two kinds of effective interactions, one of which is an extended P+QQ interaction with monopole interactions and the other is developed from a renormalized G matrix. Microscopic structures of the observed bands have been discussed with the help of the shell-model calculations.

Octupole collectivity in 94Zr

The Zr isotopes between 90Zr and 96Zr are expected to be spherical based on the almost complete subshell closures at Z = 40 and N = 50, 56. On the other hand, they have low‐lying 3− states and show the characteristics of low frequency octupole oscillation which arise as a superposition of particle‐hole excitations. A 380 MeV 94Zr beam from the tandem accelerator at the Japan Atomic Energy Agency (JAEA) was excited on a self‐supporting natPb target. The gamma‐ray detector array GEMINI‐II was used to detect deexcitation gamma rays. The scattered beam (94Zr) was detected with a position‐sensitive particle detector system. The gamma‐ray intensities were used as an input to the least‐squares search code GOSIA to determine the E3 matrix element of the first 3− excited state of 94Zr. The B(E3;0+→3−) value of 0.21(6) e2b3 in 94Zr has been obtained by Coulomb excitation experiment.