Determine the excitation energy of the long-lived isomer in 151Ce

Determine the excitation energy of the long-lived isomeric state of cerium-151, whose energy has not yet been established, to remove ambiguity in mass measurements that currently cannot resolve ground and isomeric components.

Background

The authors measured time-of-flight spectra at high resolving power (Rm ~ 500,000) but could not resolve low-lying isomers with E_X ≲ 100 keV. For 151Ce, which has a long-lived isomeric state with unknown energy, any candidate isomeric peak was not observed and the measured mass was treated as a single component, introducing ambiguity.

Establishing the excitation energy of the 151Ce isomer would enable separation of ground and isomer contributions in mass determinations and improve the reliability of mass excess values.