III. Inelastic neutron scattering in lithium seven

Abstract

The cross section for the reaction ⁷Li(nn′)⁷Li*, in which the residual nucleus is left in its first excited state (478 kev), has been measured as a function of neutron bombarding energy from the threshold up to 1·65 mev. The reaction was studied by observation, with both stilbene and sodium iodide crystal detectors, of the γ-rays from the ⁷Li*. Details of the experimental method are given. The shape of the excitation curve for the reaction immediately above threshold indicates a strong s-wave contribution due to a (1-) level in the ⁸Li compound nucleus. Above this region the curve rises to a peak at a neutron energy of about 1·35 mev, corresponding to a ⁸Li level at 3·2 mev (Γ≅1 mev), which can be interpreted in termsof theoretical models as either a (1+) or, possibly, a (1-) state.