抄録
The (n, α) reaction on 12C has been investigated by bombarding a thin polyethylene film with 14.1 MeV neutrons. The emitted α-particles were detected by a CsI(T1) scintillation detector and distinguished from other particles by applying the pulse-shape discrimination method. The angular distribution of the α-particles leaving the residual nucleus 9Be in the ground state was strongly peaked at about 40° and at the backward hemisphere in the center-of-mass angles, predicting the presence of direct interaction processes. The ground state transition cross section of 76±11 mb was obtained. The forward peaking was compared with the plane wave theory, for both the pick-up and knock-on processes. The reduced width amplitude of the α-cluster at the nuclear surface of 12C was determined by attempting the theoretical fit to the backward peak of the angular distribution in terms of the heavy-particle stripping model. Comparing this value with those obtained from other reactions on light nuclei, it seems that the α-cluster reduced width amplitudes are considerably large for the nuclei being amenable to the α-particle model such as 12C and 16O.
