Experimental study of the 11B(p,3α)γ reaction at Ep=0.5–2.7 MeV

Our understanding of the low-lying resonance structure in 12 C remains incomplete. We have used the 11 B ( p , 3 α ) γ reaction at proton energies of E p = 0.5 –2.7 MeV as a selective probe of the excitation region above the 3 α threshold in 12 C. Transitions to individual levels in 12 C were identified by measuring the 3 α final state with a compact array of charged-particle detectors. Previously identified transitions to narrow levels were confirmed and new transitions to broader levels were observed for the first time. Here, we report cross sections, deduce partial γ -decay widths and discuss the relative importance of direct and resonant capture mechanisms.