Fast Neutron Scattering Cross Sections of Sn-118 at 14.9 and 18.0 MeV

Abstract

The neutron scattering cross sections of 118Sn have been measured at incident neutron energies of 14.9 and 18.0 MeV using the JAERI tandem fast neutron time-of-flight spectrometer. Measured are the angular distributions of the elastically scattered neutrons, and of inelastically scattered neutrons to the first 2⁺ state (Q=-1.23 MeV) and to the 3^- state (Q=-2.32 MeV). The angular distributions of the inelastic scattering were strongly forward peaked. Thus the direct reaction process is dominant in this energy range. The measured angular distributions were analyzed in terms of the spherical optical model, the distorted-wave Born approximation and the coupled-channel theory. The optical potential and deformation parameters were deduced. The obtained deformation parameters were compared with other experimental results and the relation of β_{p, p'}/β_{n, n'}1 was confirmed for the quadrupole deformation. This ratio was found to be consistent with the prediction of the schematic model for treatment of core-polarization. For the octupole deformation, however, this ratio was essentially unity. Isoscaler deformation parameters were also deduced.