Investigation of particle-unbound excited states in light nuclei with resonance-decay spectroscopy using a 12Be beam

Resonance-decay spectroscopy is used to study particle-unbound excited states produced in interactions of E/A=50 MeV Be-12 on polyethylene and carbon targets. The particle-unbound states are produced in a variety of reaction mechanisms, ranging from projectile fragmentation to proton pickup. New proton-decaying excited states are observed in Li-9(E-*=14.1 +/- 0.1 MeV, Gamma=207 +/- 49 keV) and Be-10(E-*=20.4 +/- 0.1 MeV, Gamma=182 +/- 74 keV). In addition a new alpha-decaying state is observed in B-13(E-*=13.6 +/- 0.1 MeV, Gamma <= 320 keV). Also found was a Be-8 state with E-*=23 MeV, Gamma=616 +/- 30 keV, which decays to the p+H-3+alpha channel. Correlation between the fragments indicates that the decay is initiated by a proton emission to the 4.63-MeV state of Li-7 and the spin of the state is J>2. A second T=2 state was confirmed in B-12 at 14.82 MeV, which decays to the p+Be-11, H-3+Be-9, and alpha+Li-8 channels. Its width was found to be Gamma <= 100 keV and its spin is consistent with J(pi)=2(+).