Low-lying isovector2+valence-shell excitations ofPo212

We present the results from an experiment dedicated to search for quadrupole-collective isovector valence-shell excitations, states with so-called mixed proton-neutron symmetry (MSS), of $^{212}\mathrm{Po}$. This nucleus was studied in an $\ensuremath{\alpha}\text{-transfer}$ reaction. The lifetimes of two short-lived excited states, candidates for the one-phonon MSS, were determined by utilizing the Doppler shift attenuation method. The experimental results are in qualitative agreement with a simple $\text{single-}j$ shell model calculation, which, together with the observed lack of quadrupole collectivity, indicates that the isovector nature of low-lying states is a property of the leading single-particle valence shell configuration.