Various nuclear structures in Xe-140 studied by beta decay of ground and isomeric states in I-140

Structure of the neutron-rich N = 86 isotope Xe-140, located northeast of a doubly-magic nucleus Sn-132, is investigated by beta-gamma spectroscopy. Two beta-decay isomers in I-14(0) are newly found in the study of two different beta decays of I-140 which were produced by two reactions (i) direct in-flight fission at a primary target and (ii) beta decay of Te-140 at an active stopper. Half-lives of the beta decays of the ground state, the low-spin isomer, and the high-spin isomer are determined to be 0.38(2), 0.91(5), and 0.47(4) s, respectively. Decay schemes of the beta decay of the high-spin isomer and of the mixed beta decays of the ground state and the low-spin isomer in I-140 to Xe-140 are constructed using the information on gamma-ray coincidence relation and gamma-ray intensity. Nuclear structures of the low-lying states in Xe-140 and I-140 are discussed by comparing the experimental results to two theoretical calculations based on a large-scale shell model and the deformed Skyrme Hartree-Fock-Bogoliubov plus deformed quasiparticle-random-phase approximation. Possible candidates for (quasi-)gamma-band members of 2(+) and 4(+) states and the octupole collective 1(-) state are proposed in Xe-140. Increase of quadrupole, triaxial, and octupole collectivities is discussed with the increase of neutron and proton numbers.