Rotational sequences in N=98 Tm167 populated in the Dy164(Li7,4nγ)Tm167 fusion-evaporation reaction

Abstract

High spin states in $_{69}^{167}\mathrm{Tm}_{98}$ were studied using the $^{164}\mathrm{Dy}(^{7}\mathrm{Li},4n\ensuremath{\gamma})^{167}\mathrm{Tm}$ fusion-evaporation reaction. The XTU Tandem accelerator at the INFN Legnaro National Laboratory was used to accelerate a beam of $^{7}\mathrm{Li}$ ions to 55 MeV, and $\ensuremath{\gamma}$ rays from the evaporation residues were studied using the GASP Ge multidetector $\ensuremath{\gamma}$-ray array. The present data have allowed the $1/{2}^{\ensuremath{-}}[541]$ yrast sequence of $^{167}\mathrm{Tm}$ to be established to spin $61/{2}^{\ensuremath{-}}$, the $1/{2}^{+}[411]$ ground-state band to be extended to $(51/{2}^{+})$, and the $7/{2}^{+}[404]$ and $7/{2}^{\ensuremath{-}}[523]$ rotational sequences to be extended to spins $(43/{2}^{+})$ and $(39/{2}^{\ensuremath{-}})$, respectively. The experimental data have been compared with the results of cranked shell-model calculations; for the above decay sequences, crossing frequencies are in agreement with those of the neighboring even-even isotones, within experimental errors, and there is no evidence of a configuration-dependence of band crossing frequencies. Experimental $B(M1)/B(E2)$ values were extracted and compared with the results of theoretical calculations which are based on a semiclassical cranking model. Finally, the experimental high-spin decay sequences have been compared with the results of projected shell-model (PSM) calculations; agreement between experiment and theory is excellent over the complete range of spins. The calculated energy levels of the one-quasiparticle bands in $^{167}\mathrm{Tm}$ depend sensitively on the deformation parameters used in the PSM calculation.