Suppression in compound nuclear fusion at low projectile energies

In this study, the excitation functions of evaporation residues produced in the 18O + 144Sm system have been measured through offline γ ray spectrometry. The statistical model code PACE-4, ALICE91, and EMPIRE 3.2.2 were utilized to distinguish the evaporation residues populated through the compound and non-compound nuclear fusion processes. For a comprehensive investigation of fusion suppression and its correlation with the charge of the target and the Qα value of the projectile, the compound nuclear fusion cross sections of various projectile-target combinations were analyzed within the framework of the Universal Fusion Function (UFF) reduction method. The study revealed that the measured fusion functions of various systems were suppressed compared to the UFF, where the degree of suppression was dependent on the projectile’s Qα value. Besides that, an exponential increase in the suppression was further observed with increasing Qα values, while the target charge had a marginal effect. A generalized formula based on present study has been proposed to estimate fusion suppression of different systems as a function of Qα value of the projectile. The above observations indicates that the involvement of non-compound nuclear reactions leads to a reduction in the compound nuclear fusion cross section at energies above the Coulomb barrier. This is primarily attributed to the loss of flux in the compound nuclear fusion channel, which is offset by an increased flux in non-compound fusion processes.