IN-BEAM GAMMA-RAY SPECTROSCOPY OF THE N = Z + 1 NUCLEUS GA-63

A total of ten previously observed gamma rays have been assigned to the N = Z + 1 nucleus Ga-63; these provide the first information on excited states reported in this neutron-deficient system. Ga-63 has been populated using the Ca-40(Si-28, alpha-p), Ca-40(S-32, 2-alpha-p), and Ca-40(Si-29, alpha-pn) reactions at beam energies of 80-100 MeV. Particle-gamma coincidence techniques provide a definitive identification of gamma transitions in Ga-63. An yrast-level scheme is proposed on the basis of charged-particle-gamma, charged-particle-gamma-gamma, and neutron-gamma-gamma coincidences. Spin and parity assignments are based on neutrongated gamma-ray angular distributions, directional correlation with oriented nuclei ratios and systematics. Nine new energy levels are identified in addition to the previously known ground state, with the highest level at an excitation energy of 7.7 MeV. The results are interpreted in terms of the relevant single-particle orbitals and the systematics of the neighboring nuclei. In addition, a new determination has been made of the E2/M1 mixing ratio for the (5-/2)1 --> (3-/2)1 transition in Ga-65, resolving a disagreement between two previous measurements.