Nuclear spectroscopy above isomers in67148Ho81and67149Ho82nuclei: Search for core-excited states inHo149

Abstract

The excited states of $^{148}\mathrm{Ho}$ and $^{149}\mathrm{Ho}$ isotopes are studied using $\ensuremath{\gamma}$-ray and electron spectroscopy in off-beam and in-beam modes following $^{112,114}\mathrm{Sn}$($^{40}\mathrm{Ar}$,$\mathit{xnyp}$) reactions. Experiments include measurements of single $\ensuremath{\gamma}$-rays and conversion electron spectra as well as $\ensuremath{\gamma}$-$\ensuremath{\gamma}$, electron-$\ensuremath{\gamma}$, $\ensuremath{\gamma}\ensuremath{-}t$, and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}\ensuremath{-}t$ coincidences with the use of the OSIRIS-II 12-HPGe array and conversion electron spectrometer. Based on the present results, the level schemes of $^{148}\mathrm{Ho}$ and $^{149}\mathrm{Ho}$ are revised and significantly extended, up to about 4 and 5 MeV of excitation energy, respectively. Spin and parity of ${5}^{\ensuremath{-}}$ are assigned to the $9.59$-s isomer in $^{148}\mathrm{Ho}$ based on conversion electron results. Previously unobserved $\ensuremath{\gamma}$ rays feeding the ${10}^{+}$ isomer in $^{148}\mathrm{Ho}$ and the $27/{2}^{\ensuremath{-}}$ isomer in $^{149}\mathrm{Ho}$ nuclei are proposed. Shell-model calculations are performed. Possible core-excited states in $^{149}\mathrm{Ho}$ are discussed.