Unexpected Decrease in Moment of Inertia Between N = 98-100 in 162,164Gd

From γ-γ-γ coincidence studies of the prompt γ-rays emitted in the spontaneous fission (SF) of ²⁵²Cf with Gammasphere, the yrast energy levels in neutron-rich ^162,164Gd were identified for the first time from 2⁺ to 16⁺ and from 2⁺ to 14⁺, respectively. The 2⁺ level energies are 71.6 and 73.3 keV in ^162,164Gd, respectively. The transition energies from every level in ¹⁶⁴Gd are higher than those from the same levels in ¹⁶²Gd. There is a systematic decrease at every level of the moment of inertia (MOI) and similarly β₂ deformation in N = 100 ¹⁶⁴Gd compared to N = 98 ¹⁶²Gd. The minimum in E(2⁺) and maxima in MOI and β₂ occur at N = 98. This behavior is unexpected compared to the E(2⁺) and β₂ trends in Er, Yb, and Hf nuclei where the minima and maxima occur at neutron midshell, N = 104.