Experimental probe on the production of $^{97}$Ru from $^{7}$Li+$^{93}$Nb reaction: A study on the precompound emissions

Abstract

Background: Interaction of weakly bound heavy-ions with an intermediate or heavy target is not yet understood completely due to the scarcity of experimental data. In order to develop a clear understanding of breakup fusion or preequilibrium emission even at low energy range, 3--10 MeV/nucleon, more experimental investigations are necessary. Purpose: Study of reaction mechanisms involved in the weakly bound heavy-ion induced reaction, $^7$Li + $^{93}$Nb, at low energies by measuring the production cross sections of the residual radionuclides. Method: Natural niobium ($^{93}$Nb) foil, backed by aluminium (Al) catcher, arranged in a stack was bombarded by $^{7}$Li ions of 20-45 MeV energy. Activity of the residues produced in each $^{93}$Nb target was measured by off-line $γ$-ray spectrometry after the end of bombardment (EOB) and cross sections were calculated. Experimental cross sections were compared with those computed using compound and precompound models. Results: In general, measured excitation functions of all residues produced in $^{7}$Li + $^{93}$Nb reaction showed good agreement with the model calculations based on Hauser-Feshbach formalism and exciton model for compound and precompound processes, respectively. Significant preequilibrium emission of neutrons was observed at the relatively high energy tail of the excitation function of $^{97}$Ru. Conclusions: Preequilibrium process played an important role for the enhancement of cross-section in $xn$ reaction channel over the compound reaction mechanism at higher energies for $^{7}$Li + $^{93}$Nb reaction. Additionally, indirect evidence of incomplete or breakup fusion was also perceived.