Shell Model Study of the Yrast Structure in ⁹⁸ Nb

Gamma-ray transitions from excited states in 98 Nb have been reported in Ref., 1 and the yrast level scheme up to an excitation energy of 3034 keV has been established in Ref.2 However, a detailed theoretical interpretation of these structures is still lacking. In the present work, the yrast states of 98 Nb are investigated using large-scale shell-model calculations within the jj45pn model space employing the jj45pna effective interaction. To examine the role of the neutron 1h 11/2 orbital on the nuclear structure, calculations were performed using two truncation schemes: one excluding the 1h 11/2 orbital and the other allowing a maximum occupancy of two neutrons in the 1h 11/2 orbital. The inclusion of the νh 11/2 orbital has only a minor influence on the low-spin states but significantly modifies the higher-spin positive- and negative-parity states. A comparison of the root-mean-square deviation values indicates that excluding the νh 11/2 orbital yields a slightly better description of the low-spin yrast states. The predicted (B(E2)) and (B(M1)) transition strengths further support the proposed microscopic structure.