OBSERVATION OF FERMI SUPERALLOWED BETA(-ODD, N=Z NUCLEI - EVIDENCE FOR 0(+) GROUND-STATES IN Y-78, NB-82, AND TC-86() DECAYS IN HEAVY ODD)

The beta(+)-decay half-lives of the neutron-deficient, odd-odd, N = Z nuclei Rb-74, Y-78, Nb-82, and Tc-86 have been measured following the fragmentation of a primary Mo-92 beam at an energy of 60 MeV per nucle on. The half-lives were measured by correlating beta(+) decays with th e implantation of unambigously identified fragments. The deduced log f t values are consistent with 0(+) --> 0(+) Fermi superallowed transiti ons, which together with the measured beta(+) detection efficiencies s uggest T = 1, I-pi = 0(+) ground states for these odd-odd, N = Z nucle i. These data represent the heaviest N = Z systems for which Fermi sup erallowed decays have been established. The results suggest that these nuclei can extend the mass range used to test the conserved vector cu rrent hypothesis of the standard model. [S0031-9007(98)07389-X].