Thulium-169 neutron inelastic scattering cross section measurements via the Tm-169(n, n 'gamma) reaction

Neutron inelastic scattering from thulium-169 has been studied for states a bove 100 keV via the (n, n'gamma) reaction at incident energies in the 0.2- to 1.0-MeV range. A high-resolution Ge spectrometer in conjunction with th e time-of-flight technique was utilized. Thirty-six gamma-ray transitions f rom 16 levels were observed. Gamma-ray angular distributions were measured at E-n = 750 keV and excitation functions at 125 degrees were measured in 5 0 keV steps over the range of incident energies. Differential gamma-ray pro duction cross sections and gamma-ray branching ratios were obtained. Inferr ed neutron inelastic level cross sections of the four lowest groundstate ro tational band (K-pi = 1/2(+)) members are compared to the sum of calculated compound nucleus and direct interaction cross sections. For the remaining levels, measurements are compared to compound nucleus calculations only. Th e comparison shows generally good agreement particularly near threshold. (C ) 2000 Elsevier Science B.V. All rights reserved.