Level structure ofGd155and the electron-capture decay ofTb155

The decay of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tb}$ to levels of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$ has been studied by $\gamma$-ray and conversion-electron spectroscopy with mass-separated sources. Below 660 keV, approximately 150 $\gamma$ rays have been observed and assigned to a level scheme with 28 levels. The mixing of even-parity levels is calculated using a variation plus diagonalization procedure. The resultant wave functions are used to calculate transition probabilities and magnetic moments, which are compared with the experimental results. $\beta -$ and $\gamma -$ vibrational states are identified and compared with corresponding excitations in neighboring even-even nuclei.