Identification of the $\gamma$-vibrational band built on the $11/2^{-}\left[505\right]$ orbital in ${}^{165}$Er

Excited states in ${}^{165}$Er have been populated using the ${}^{160}$Gd(${}^9$Be, 4$n$) reaction at beam energies of 42 and 45 MeV. A band consisting of two levels at excitation energies of 1317.6 and 1505.9 keV, both of which decay strongly to the $11/2^{-}\left[505\right]$ band, is observed and assigned as the $\gamma$-vibrational band built on the $11/2^{-}\left[505\right]$ configuration. In addition, a newly identified level is proposed as a three-quasiparticle state.

Figure 1

Partial level scheme of ${}^{165}$Er deduced from the present work.

Figure 2

The $\gamma$-ray spectra gated on the (a) 155.7- and (b) 317.0-keV transitions. The asterisks indicate the contaminant lines, which are in coincidence with the 314.9-keV transition in ${}^{164}$Er or the 315.4-keV transition in ${}^{162}$Dy.