l-forbidden Gamow-Teller beta decay of Cu-57

Abstract

Absolute branching ratios for the beta decay of Cu-57 to excited states up to 3.3 MeV in Ni-57 have been determined, including the rho-forbidden Gamow-Teller transition to the first excited state in Ni-57. Four transitions to excited states at 0.768, 1.113, 2.443, and 3.007 MeV are observed in addition to the superallowed decay to the ground state of Ni-57. The, measured branching ratio to the ground state is 89.9 +/- 0.8% and the branching ratios to the four excited states are 0.94 +/- 0.09%, 8.6 +/- 0.6%, 0.17 +/- 0.03%, and 0.35 +/- 0.04%, respectively. In addition we have measured the Cu-57 half-life and find it to be 196.3 +/- 0.7 ms, which is in good agreement with the most recent measurement. B(GT) values have been extracted from the new results and are compared to shell model calculations.