Isomeric fission yield ratios for odd-mass Cd and In isotopes using the phase-imaging ion-cyclotron-resonance technique

Abstract

Isomeric yield ratios for the odd-$A$ isotopes of $^{119--127}\mathrm{Cd}$ and $^{119--127}\mathrm{In}$ from 25-MeV proton-induced fission on natural uranium have been measured at the JYFLTRAP double Penning trap, by employing the phase-imaging ion-cyclotron-resonance technique. With the significantly improved mass resolution of this novel method isomeric states separated by 140 keV from the ground state, and with half-lives of the order of 500 ms, could be resolved. This opens the door for obtaining new information on low-lying isomers, which are important for nuclear structure, fission, and astrophysics. In the present work the experimental isomeric yield ratios are used for the estimation of the root-mean-square angular momentum ${J}_{\mathrm{rms}}$ of the primary fragments. The results show a dependency on the number of unpaired protons and neutrons, where the odd-$Z$ In isotopes carry larger angular momenta. The deduced values of ${J}_{\mathrm{rms}}$ display a linear relationship when compared with the electric quadrupole moments of the fission products.