Pairing effects and multistep direct and compound emission in theMo92−100(p,xn) reactions

The reactions ${}_{}{}^{92}{}_{}{}^{}$,94,95,96,97,9 ${}_{}{}^8{}_{}{}^{}$,100Mo(p,xn) have been studied with $E_{\mathrm{p}=25.6\mathrm{}}$ MeV protons for neutron angles 3?(de≤${\mathrm{CTHETA}}_{\mathrm{n}\mathrm{\le }177}$°. In the preequilibrium region the angle integrated, inclusive neutron energy spectra show pronounced pairing effects that seem to be correlated with the ground state deformation. The angular distributions show more backward yield than predicted by semiclassical preequilibrium models. A quantitative description is obtained with a quantum-mechanical statistical multistep model including three steps of direct and compound plus subsequent equilibrium emission. Both components are calculated consistently with a Yukawa-type residual interaction of strength $V_0$=25 MeV.