Beta-decay energies and masses of short-lived isotopes of rubidium,caesium, francium,and radium

Total decay energies have been measured for a number of neutron-deficient Rb and Cs isotopes, as well as for some neutron-rich isotopes of Fr and Ra. Mass separated sources were produced at the ISOLDE on-line separator at CERN. By applying two differentβ-γ coincidence methods,Q values or their lower limits were determined for^76–78Rb,⁸⁰Rb,^121–124Cs,²²²Fr,^224–226Fr,²²⁹Ra-²²⁹Ac. For many of these nuclei, the atomic mass excesses could be derived, allowing the comparison of masses of far unstable nuclei with predictions from mass formulae. The odd-odd nuclei⁷⁶Rb and⁷⁸Rb appear to be 1?1 1/2 MeV more strongly bound than expected from the systematics.