Total β-decay energies and masses of short-lived isotopes of zinc, gallium, germanium and arsenic

Experimental total β-decay energies for short-lived isotopes of zinc, gallium, germanium and arsenic are presented. The sources were produced as mass-separated fission products at the OSIRIS on-line separator at Studsvik. By applying β-γ coincidence methods, Qsub(β) values were determined for 75-78Zn, 76-79Ga, 7980Ge and 808183As. For these nuclei close to the shell N=50 and in the vicinity of the r-process 'seed', the atomic mass excess could be derived, allowing the comparison of masses of very neutron-rich unstable nuclei with predictions from mass formulae. (Auth.)