Proton-neutron symmetry in valence mirror nuclei.

Nuclear states of yrast and yrare type have been investigated in pairs of valence mirror nuclei: {sup 110}Sn-{sup 142}Nd, {sup 114}Sn-{sup 146}Gd, {sup 43}Ca-{sup 51}V, {sup 45}Ca-{sup 53}Mn, as well as in some even calcium isotopes with their corresponding {ital N}=28 valence mirror isotones. The observed similarities can be related to an approximate proton-neutron symmetry in valence mirror nuclear states.