PREEQUILIBRIUM EMISSION IN (P, XN) REACTIONS ON PALLADIUM ISOTOPES

Energy spectra of neutrons from the Pd-104, 105, 106, 108, 110(p, xn) reactions at E(p) = 26.1 MeV have been measured using the time-of-flight technique with good overall energy resolution (< 250 keV). The hard part of angle-integrated spectra corresponding to low residual excitations (U less-than-or-equal-to 6 MeV) exhibits pronounced structure varying from isotope to isotope. The observed structure can be reasonably well described by preequilibrium-model calculations with two-quasiparticle state densities for proton-particle neutron-hole configurations based on Nilsson-model single-particle levels instead of equidistant ones. The influence of nuclear deformation and pairing on preequilibrium particle emission is explored.