Investigation of the fusion mechanism in the Li6 -induced reaction on Nb93

Abstract

We attempt to put forth the competing reaction mechanisms through residual cross section measurement in $^{6}\mathrm{Li}$ fusion with $^{93}\mathrm{Nb}$. The measured residual cross sections in the 24--43 MeV energy range are analyzed with the theoretical estimations from pace4, empire3.2.2, and alice23 statistical model codes. The replication of major $xn$-channel cross sections by empire with enhanced generalized superfluid model (EGSM) level density confirms that the population of $xn$-channel residues is through the complete fusion (CF) mechanism. The preequilibrium (PEQ) emission signatures were witnessed in the case of $^{97}\mathrm{Ru}$ residue populated via the $2n$ channel. Amplification of major experimental $p$- and $\ensuremath{\alpha}$-channel cross sections relative to the optimal theory was interpreted by considering the possibility of an incomplete fusion (ICF) process in addition to CF, owing to the low breakup threshold of the $^{6}\mathrm{Li}$ projectile. Thus, the ICF strength fraction $({F}_{\mathrm{ICF}})$ was estimated. The ${F}_{\mathrm{ICF}}$ turned out to be $\ensuremath{\approx}8--20%$ with an increasing trend and is found to be thoroughly higher than the deduced ${F}_{\mathrm{ICF}}$ for $^{7}\mathrm{Li}$ reaction on $^{93}\mathrm{Nb}$ target. In the case of weakly bound $^{6,7}\mathrm{Li}$-induced reactions, the first attempt is made to understand the influence of entrance channel parameters such as bombarding energy, $\ensuremath{\alpha}$-separation energy, Coulomb factor, mass asymmetry, neutron skin thickness, angular momentum, etc., on ${F}_{\mathrm{ICF}}$. The observed trend of the isomeric cross section ratios from the relative population of isomeric and ground states of $^{96,94}\mathrm{Tc}$ radionuclides is also discussed.