PICOSECOND LIFETIME MEASUREMENT OF NEUTRON CORE-EXCITED STATES IN THEN=50 NUCLEUS RH-95

Lifetimes of high-spin states in the N = 50 nucleus Rh-95 were measure d using the recoil-distance Doppler-shift technique. The nuclei were p roduced via the reaction Ni-58(Ca-40,3p) at 145 MeV beam energy and th e gamma radiation was detected in six EUROBALL cluster detectors. Redu ced transition probabilities for seventeen gamma transitions and limit s for nine further transitions were extracted and compared with the pr edictions of the spherical shell model based on the extended configura tion space, (0f(5/2) 1p(3/2), 1p(1/2), 0g(9/2)) for protons and (0g(9/ 2), 1d(5/2)) for neutrons relative to a hypothetical Ni-68 core. The r esults indicate that all observed states with 27/2 less than or equal to I less than or equal to 39/2 are built from a neutron g(9/2) --> d( 5/2) excitation across the N = 50 shell closure, coupled to up to five valence protons in different configurations. Evidence of stretched di pole cascades having large M1 strengths was found and explained by spi n recoupling within the nu(g(9/2))(-1)nu(d(5/2)) neutron part of the w avefunctions, (C) 1998 Elsevier Science B.V.