Nuclear structure of 166 Ho studied in neutron-capture, ( d , p ) , and ( d , 3 He ) reactions

The nucleus ${}^{166}\mathrm{Ho}$ was studied with thermal and average resonance neutron capture and with $(d,p)$ and ${(d,}^{3}\mathrm{He})$ reactions. We have devoted a large effort to the measurements of $\ensuremath{\gamma}\ensuremath{\gamma}$-coincidence spectra in the broad energy interval 50\char21{}6243 keV. From these data and those of previous studies, the level scheme has been developed containing levels grouped into 23 rotational bands below 1 MeV. Of these, six bands are new and several others, known previously, have been modified and expanded based upon our experimental data. In all, 32 new levels have been identified. Of particular note has been the identification of two rotational bands whose underlying structure consists of $\ensuremath{\gamma}$-vibrational states built upon the two lowest energy quasiparticle states in ${}^{166}\mathrm{Ho}.$ Two new Gallagher-Moszkowski matrix elements were determined: ${E}_{\mathrm{GM}}{(p7/2}^{\ensuremath{-}}[523]\ifmmode\pm\else\textpm\fi{}{n5/2}^{\ensuremath{-}}[523])=\ensuremath{-}108.5$ keV and ${E}_{\mathrm{GM}}{{(p7/2}^{\ensuremath{-}}[523]\ifmmode\pm\else\textpm\fi{}{n7/2}^{+}[633])\ensuremath{\mp}{Q}_{22}}=+138.2$ keV. The resultant level scheme is in good agreement with semiempirical and quasiparticle phonon models where residual interactions have been taken into account. Suggestions are given for further experimentation on ${}^{166}\mathrm{Ho}$ level structure using existing technology.