  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 $\gamma$-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.
