Measurement and theoretical analysis of neutron elastic scattering and inelastic reactions leading to a three-body final state for [Formula Presented] at 10 to 20 MeV

The neutron elastic and inelastic scattering double-differential cross sections of [Formula Presented] were measured at incident neutron energies of 11.5, 14.1, and 18.0 MeV. A phenomenological neutron optical model potential of [Formula Presented] was constructed to describe the total and elastic scattering cross sections from 5 MeV to several tens MeV, based on the present data together with information from other works. This potential was found to describe the inelastic scattering to the first excited state [Formula Presented] well via the distorted-wave Born approximation (DWBA) calculation with the macroscopic vibrational model. The continuum neutron energy spectra and angular distributions were then analyzed by the theory of final-state interaction extended to the DWBA form, with an assumption that the [Formula Presented] interaction is dominant in the three-body final state consisting of [Formula Presented] and α particles. Such a calculation was found to be successful in explaining the major part of the low-excitation neutron spectra and angular distribution down to the Q-value region of [Formula Presented] except for the Q-value range where the [Formula Presented] quasifree scattering will give a non-negligible contribution at forward angles.