Electromagnetic properties of the11/2−states inSn111andSn113

In order to study the core polarization effects in medium heavy spherical nuclei the mean lives and $g$ factors of the ${11/2}^{-}$ states in ${}_{}{}^{111}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{113}{}_{}{}^{}\mathrm{Sn}$ have been measured. The isomeric states were populated by the ${}_{}{}^{111}{}_{}{}^{}\mathrm{Cd}(\alpha ,2n){}_{}{}^{113}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{107,109}{}_{}{}^{}\mathrm{Ag}({}_{}{}^7{}_{}{}^{}\mathrm{Li},3n){}_{}{}^{111,113}{}_{}{}^{}\mathrm{Sn}$ reactions with pulsed $\alpha$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ beams. The nuclear spin precession in the 60 kG field of an on-line superconducting magnet was observed time differentially. The following values were obtained: ${}_{}{}^{111}{}_{}{}^{}\mathrm{Sn}$ ${(11/2\mathrm{}}^{-}$, 979.6 keV): $\tau =13.3\mathrm{}\left(15\right)\mathrm{}$ ns, $g=-0.23\mathrm{}\left(2\right)\mathrm{}$; ${}_{}{}^{113}{}_{}{}^{}\mathrm{Sn}$ ${(11/2\mathrm{}}^{-}$, 740 keV): $\tau =118.5\mathrm{}\left(25\right)\mathrm{}$ ns, $g=-0.235\mathrm{}\left(4\right)\mathrm{}$. The magnetic moments of the ${11/2}^{-}$ states in ${}_{}{}^{111,113,115,119}{}_{}{}^{}\mathrm{Sn}$ and their near constancy as a function of mass number are reproduced by a first order $M1\mathrm{}$ core polarization calculation using pairing model wave functions, experimentally determined energy denominators, and occupancy parameters. The strong reduction of the $M2\mathrm{}$ rates for the $h_{\frac{11}{2}}\to g_{\frac{7}{2}}$ transition as compared to the single particle estimate shows the destructive effect of the spin-isospin $M2\mathrm{}$ core polarization.