The decays of the three isomers of ${}^{131}\mathrm{In}$ and the total decay energies of the two isomers of ${}^{131}\mathrm{Sn}$ have been studied in high sensitivity experiments at the OSIRIS mass separator. The main purpose of the investigation was to determine the position of the neutron hole $h_{11∕2}$ state, since a previous determination appeared to be in error. The present results support a small separation of the $d_{3∕2}$ and $h_{11∕2}$ neutron hole states. The new value obtained from measurements of decay energies is $69\pm 14\mathrm{keV}$. A more precise value of $65.1\mathrm{keV}$ may be deduced from the level scheme of ${}^{131}\mathrm{Sn}$ obtained currently, however without firm support from coincidence data. This relatively low excitation energy of the $h_{11∕2}$ state is in agreement with systematics and in disagreement with the previous determination. A re-evaluation of the $Q_{\beta }$ values and isomer spacings of ${}^{131}\mathrm{In}$ has been made.

• Received 4 June 2004

DOI:https://doi.org/10.1103/PhysRevC.70.034312