Role of the pre-equilibrium particle emission in the ${}^{249-251}$No production in the ${}^{204}$Pb(${}^{48}$Ca, xn)${}^{252-x}$No reaction

Abstract

Experimental data on the production of ${}^{250}$No in its ground and isomeric states in the ${}^{204}$Pb(${}^{48}$Ca,2n)${}^{250}$No reaction at ${}^{48}$Ca beam energies from 200 to 240 MeV are analyzed within a unified approach combining the Hauser--Feshbach statistical model and the Griffin exciton model, assuming the emission of one pre-equilibrium particle. The influence of pre-equilibrium processes on the production cross sections of the ${}^{249-251}$No isotopes is investigated. The inclusion of pre-equilibrium light-particle emission significantly improves the description of the measured production cross sections, particularly in the high-energy region, where differences of several orders of magnitude are obtained, and for the population of the ground and isomeric states of ${}^{250}$No. The proposed approach also reproduces the observed incident-energy dependence of the residual-nucleus production cross sections.

Comments: 7 pages, 5 figures, 32 references