The B10(d, α)Be8 reaction and the 2.94 MeV state in Be8

Abstract

Alpha particles from the reaction B10(d, α)Be8 were observed with solid state particle detectors and a 256-channel pulse-height analyser. The differential cross section of the reaction was measured at 156° in the laboratory system. For the reaction channel leading to the ground state of Be8, the differential cross section increased steadily from approximately 0.28 to 0.39 mb/sr over the deuteron energy range from 1.0 to 1.8 MeV. Over the same energy range the differential cross section for the reaction channel leading to the 2.94 MeV, first excited state of Be8 increased from 2.62 mb/sr to a maximum of 5.54 mb/sr at Ed = 1.6 MeV and then decreased to 4.88 mb/sr. Angular distributions of the particle groups leading to both the ground and first excited states of Be8 were measured at five energies in the range Ed = 1.0 to 1.8 MeV. Forward peaking with an energy dependent second maximum at approximately 115° was observed. For the ground state transition, total cross sections are 7.5 mb, 7.2 mb, 6.75 mb, 9.2 mb and 9.3 mb at deuteron energies of 1.0, 1.2, 1.46, 1.59 and 1.75 MeV, respectively. The cross sections for the transition to the first excited state at the same deuteron energies are 50 mb, 59 mb, 61 mb, 71 mb and 60 mb, respectively. A careful search for possible even parity, even spin states of Be8 was made in the range of 1–7 MeV excitation energy in Be8. No evidence for states other than the 2.94 MeV, 2+ state was found. The line shape of the 2.94 MeV state was obtained with a coincidence technique. Theoretical fits of this shape were made with the Wigner-Eisenbud formalism. The results seem to indicate that, in the energy range studied, the interaction radius of two α-particles is comparatively large, i.e., from 5 to 6 fm.