Decay properties of long-lived isomers in the odd-oddN=81nucleusTb146compared to theHo148andTm150nuclei

Abstract

Excited states of the $^{146}\mathrm{Tb}$ nucleus have been studied using $\ensuremath{\gamma}$-ray and electron spectroscopy in off-beam and in-beam modes following $^{112}\mathrm{Sn}$($^{40}\mathrm{Ar}$,$3n3p$) reaction with the use of the OSIRIS-II, HPGe detector array and the conversion electron spectrometer. The multipolarity of the 343 keV transition deexciting the $({7}^{\ensuremath{-}})$ level in $^{146}\mathrm{Tb}$ shows mainly an $E2$ nature and the first excited state above the 23 s isomer is assigned as a $({5}^{\ensuremath{-}},{6}^{\ensuremath{-}})$ state. The log $\mathit{ft}$ values have been deduced for 11 ${\ensuremath{\beta}}^{+}/$EC transitions populating excited states in $^{146}\mathrm{Gd}$. The systematic behavior of spins and parities of the long-lived levels at $0+x$ keV and the first excited states above them in the $N=81$ isotones $^{146}\mathrm{Tb}$, $^{148}\mathrm{Ho}$, and $^{150}\mathrm{Tm}$ is discussed.