Nuclear Structure and Decay Data for A = 166 Isobars

Abstract

Evaluated spectroscopic data and level schemes are presented for ¹⁶⁶(Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, and Pt) isotopes, based on the measured decay and nuclear reaction studies. This evaluation for A=166 supersedes the earlier one by C.M. Baglin ([2008Ba14]). About 540 new gamma transitions and 200 excited levels are adopted in this evaluation from new measurements, compared to those in the previous evaluation. The new gammas and levels mostly belong to ¹⁶⁶Er, ¹⁶⁶Ta, ¹⁶⁶Re, and ¹⁶⁶Os nuclides, studied mainly by (HI,x) reactions and decay (mostly ¹⁶⁶Ho to ¹⁶⁶Er). In ¹⁶⁶Tm, the energy of the isomeric state with t_1/2=348 ms is not known yet, there are different assumptions in [1996Dr07] and [2002Ca46]. Also there is an ambiguity in ¹⁶⁶Re, whether the unknown level labeled as 0.0+x represents the ground state or an excited state. New measurements are needed to resolved the issues of these low lying levels in ¹⁶⁶Tm and ¹⁶⁶Re.

Throughout this evaluation, rotational band parameters are calculated from the standard energy equation:$E(J,K)=E_0+A\left[J\right(J+1)+{\delta }_{K,1/2}{(-1)}^{J+1/2}a(J+1/2\left)\right]+B{J}^2{(J+1)}^2$ where A is given in keV, B is given in eV, and the decoupling constant a is dimensionless. When not explicitly stated, B is assumed to be 0. The minimum number possible of the lowest energy levels was used to calculate each set of parameters, unless noted otherwise.