Isomer spectroscopy in 133Ba and high-spin structure of 134Ba

Abstract

The transitional nuclei 134 Ba and 133 Ba are investigated after multinucleon transfer employing the high-resolution Advanced GAmma Tracking Array coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and after fusion-evaporation reaction at the FN tandem accelerator of the University of Cologne, Germany. The Jπ = 19 / 2 + state at 1942 keV in 133 Ba is identified as an isomer with a half-life of 66.6 ( 20 ) ns corresponding to a B(E1) value of 7.7 ( 4 ) × 10 − 6 e 2 fm 2 for the Jπ = 19 / 2 + to Jπ = 19 / 2 − transition. The level scheme of 134 Ba above the Jπ = 10 + isomer is extended to approximately 6 MeV. A pronounced backbending is observed at ℏ ω = 0.38 MeV along the positive-parity yrast band. The results are compared to the high-spin systematics of the Z=56 isotopes. Large-scale shell-model calculations employing the GCN50:82, SN100PN, SNV, PQM130, Realistic SM, and EPQQM interactions reproduce the experimental findings and elucidate the structure of the high-spin states. The shell-model calculations employing the GCN50:82 and PQM130 interactions reproduce alignment properties and provide detailed insight into the microscopic origin of this phenomenon in transitional 134 Ba .