Core Excitations in Nondeformed, Odd-A, Nuclei

The possibility of describing some excited states of odd-$A$ nuclei in terms of excitations of the even-even core is investigated. No assumption is made on the nature of the core excitation, but certain relations involving electromagnetic transitions and moments are deduced. These seem to fit well some data available on ${\mathrm{Ag}}^{107}$, ${\mathrm{Ag}}^{109}$, ${\mathrm{Au}}^{197}$, ${\mathrm{Hg}}^{199}$, ${\mathrm{Tl}}^{203}$, and ${\mathrm{Tl}}^{205}$. More experimental data are required to test the validity of this picture in other cases.