Towards a satisfactory microscopic description of 2₁⁺ g factors

We investigate the possibility that microscopic boson g factor estimates may require revision and consider the impact on 2₁⁺ g factors of the difference ε_v between the neutron and proton d boson energies found typically in microscopic evaluations of interacting boson model parameters. We recalculate microscopic estimates for both d and g boson g factors, this time using the similarity-transformed Dyson boson mapping approach. Modulo more pronounced variation at the beginning and end of shells, our results confirm previous estimates by other methods. Differences between d and g boson factors are too small for the inclusion of g bosons to have a significant effect on 2₁⁺ g factor predictions. Instead, we present qualitative and semiquantitative arguments in support of the contention that microscopic estimates of ε_v (taken in conjunction with our microscopic boson g factors) can, by and large, account for the systematics of 2₁⁺ g factors in the Z=50-to-82 and N=82-to-126 shells. Detailed calculations for ¹⁴⁸Sm and ¹⁵⁴Sm are consistent with this assertion provided the Majorana interaction strength ξ₂ is negligible. Our detailed calculations suggest substantial F-spin admixtures in the 2₁⁺ states of ¹⁴⁸Sm (at the 20% level or more) and the members of ground-state band of ¹⁵⁴Sm (9% or so), and point to the existence of a mixed-symmetric β bandhead in ¹⁵⁴Sm at below 2 MeV.