Investigation of isomeric states in Rf255

Abstract

Using the GABRIELA detector array, $\ensuremath{\gamma}$-ray and internal-conversion-electron decay spectroscopy has been performed on $^{255}\mathrm{Rf}$ nuclei that were produced via the $^{207}\mathrm{Pb}(^{50}\mathrm{Ti},2n)^{255}\mathrm{Rf}$ fusion-evaporation reaction using the SHELS velocity filter. Three isomers were identified in $^{255}\mathrm{Rf}$ with the aid of Geant4 simulations. The existence of two high-$K$ isomeric states in cascade has been confirmed. Possible three-quasiparticle configurations involving the coupling of the unpaired $9/{2}^{\ensuremath{-}}[734]$ neutron to two-quasiparticle states have been suggested and a likely decay scenario has been proposed on the basis of comparisons to Geant4 simulations. The simulations have also confirmed the existence of the $5/{2}^{+}[622]$ spin isomer at low excitation energy.