ACTIVATION CROSS-SECTIONS AND ISOMERIC RATIOS IN REACTIONS INDUCED BY14.5 MEV NEUTRONS ON SM-152, SM-154 AND HF-178

Cross sections for the reactions Sm-152(n, p)Pm-152g, Pm-m1, Pm-m2, Sm -154(n, p)Pm-154g, Pm-m, Hf-178(n, p)178m,g Lu, Sm-154(n, d)Pm-153 and Sm-152(n, alpha)Nd-149 were measured at 14.5 MeV neutron energy by th e activation method. On the basis of these cross sections, the associa ted isomeric ratios in Pm-154, Pm-152, Lu-178 and the comparison with the predictions of different compound and precompound models, conclusi ons are drawn about the role of the preequilibrium processes in 14.5 M eV neutron induced reactions. Calculations for equal angular momentum removal by equilibrium and preequilibrium emitted particles better rep roduced the experimental isomeric ratios, than for higher angular mome ntum removal in the preequilibrium phase. The isomeric ratios may be u sed as a source of additional information about the spin of the isomer ic states in Pm-152 and Pm-154 for which the spectroscopic information is uncertain.