Mössbauer-Effect Studies of the 97-keV Level ofEu153

The recoilless absorption spectra of the 97-keV $\gamma$ rays from ${\mathrm{Eu}}^{153m}$ in ${\mathrm{Eu}}^{153}$ situated in ${\mathrm{Eu}}_2$ ${\mathrm{O}}_3$, in EuS${\mathrm{O}}_4$, and in europium iron garnet (EuIG) were measured at 20°K. The source used was ${\mathrm{Gd}}^{153}$ in the form of an oxide at 20°K. With the ${\mathrm{Eu}}_2$ ${\mathrm{O}}_3$ and EuS${\mathrm{O}}_4$ absorbers, unsplit absorption lines were obtained. From their widths, a value of (2.14±0.2) × ${10}^{-10\mathrm{}}$ sec was deduced for the half-life of the 97-keV level. Two alternative values for the magnetic moment of the 97-keV level of ${\mathrm{Eu}}^{153}$, (+3.21±0.22) nm and (-0.52±0.22) nm, fitted the broadened absorption line obtained with the EuIG absorber. One of the values, (+3.21±0.22) nm, is in agreement with the predictions of the unified model.