Excited states of 8Be populated via the p(7Li, 4He)4He and p(7Li, 4He*)4He resonant reactions

Abstract

A measurement of the p(7Li, 4He)4He resonant reaction on a thick mylar target was used to probe resonances in 8Be in the excitation energy range 20–25 MeV. The 7Li beams, of energies 25.8 and 58 MeV, were stopped in the target and the resulting α-particles were detected at zero degrees. Evidence was found for resonances at ∼20 and ∼25 MeV with Jπ = 0+ and 2+ character, respectively. A simultaneous measurement of the p(7Li, 4He* → p + t)4He reaction was performed, in which one of the two final-state α-particles was produced in the 20.2 MeV excited state. These events were observed to arise from an excitation energy region 23–25 MeV and have been associated with the decay of the 25.2 MeV 2+ 8Be resonance. The 25.2 MeV resonance is found to have a dominant 4He + 4He* reduced width.