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

Cross sections for the reactions¹⁵²Sm(n, p)^152g,m1,m2 Pm,¹⁵⁴Sm(n, p)^154g,m Pm,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.