Characteristics of the 21/2+ isomer in 93Mo: Toward the possibility of enhanced nuclear isomer decay

To discuss whether an enhanced isomer decay is a preferred process in a plasma environment it is required to know the structure of the isomer as well as the nearby states. The spin-21/2, 6.85-hour high-spin isomer in Mo-93 is investigated within a shell model which well describes nuclei in this mass region. By using the obtained wave-functions which correctly reproduce the observed B(E2), B(E4), and B(M1) transitions, characteristics of the isomer are shown in comparison with the isomeric states in neighboring nuclei. Calculations suggest that these high-spin isomers are formed with almost pure single-particle-like configurations. The Mo-93 21/2(+) isomer has the predominant configuration pi(g(9/2))(8)(2) circle times nu d(5/2) lying below the 15/2(+), 17/2(+), and 19/2(+) states due to neutron-proton interaction, which is the physical origin of its long lifetime. The key E2 transition that connects the 21/2(+) isomer to the upper 17/2(+) level is predicted to be substantial (3.5 W.u.), and therefore there is a real prospect for observing induced isomer deexcitation. (C) 2010 Elsevier B.V. All rights reserved.