Activation cross sections and isomeric ratios in reactions induced by 14.5 MeV neutrons on152Sm,154Sm and178Hf

Abstract

Cross sections for the reactions152Sm(n, p)152g,m1,m2Pm,154Sm(n, p)154g,mPm,178Hf(n, p)178m,g Lu,154Sm(n, d)153Pm and152Sm(n, α)149Nd were measured at 14.5 MeV neutron energy by the activation method. On the basis of these cross sections, the associated isomeric ratios in154Pm,152Pm,178Lu and the comparison with the predictions of different compound and precompound models, conclusions are drawn about the role of the preequilibrium processes in 14.5 MeV neutron induced reactions. Calculations for equal angular momentum removal by equilibrium and preequilibrium emitted particles better reproduced the experimental isomeric ratios, than for higher angular momentum removal in the preequilibrium phase. The isomeric ratios may be used as a source of additional information about the spin of the isomeric states in152Pm and154Pm for which the spectroscopic information is uncertain.