A search for proton decay from a predicted ${\frac{19}{2}}^{-}$ isomer of ${}^{77}\mathrm{Rb}$ has been performed. Products of the ${}^{40}{\mathrm{C}\mathrm{a}+}^{40}\mathrm{Ca}$ reaction at average laboratory bombardment energies of 145 and 160 MeV were transported by a helium jet to an array of particle-identification telescopes. No evidence of proton emission from the predicted isomer was observed. In a second measurement, mass 77 residues of the ${}^{40}{\mathrm{C}\mathrm{a}+}^{\mathrm{nat}}\mathrm{Ca}$ reaction at an average laboratory bombardment energy of 132 MeV were separated using the on-line mass separator RAMA. The yields of ${}^{77}\mathrm{Rb}$ and ${}^{77}\mathrm{Sr}$ were monitored by observation of beta-delayed gamma rays; $1.6\times {10}^6$ atoms of ${}^{77}\mathrm{Rb}$ were transported to the detectors. A single particle-identification telescope subtending 23% of 4π sr again showed no evidence of proton emission from the predicted isomer.

• Received 22 December 1997

DOI:https://doi.org/10.1103/PhysRevC.57.2222