Role of break-up processes in the fusion of the12C+52Crsystem

Abstract

We present the results and analysis of our investigation of the role of break-up processes on the fusion of a ${}^{12}$C${}^{6+}$ beam with a ${}^{52}$Cr target near, at, and above the Coulomb barrier. In this experiment the excitation functions of evaporation residues produced via (${}^{12}$C, 2$n$), (${}^{12}$C, pxn), (${}^{12}$C, \ensuremath{\alpha}$xn$), and (${}^{12}$C, \ensuremath{\alpha}pxn) channels in a ${}^{12}$C $+$ ${}^{52}$Cr reaction were measured at several beam energies ranging from \ensuremath{\approx}51 to 87 MeV by employing the recoil catcher technique followed by off-line \ensuremath{\gamma}-ray spectrometry. The measured excitation functions were compared with theoretical values obtained using the pace4 statistical model code. Further, for a (${}^{12}$C, $p$2$n$) channel the measured excitation function was compared with the predictions of the alice-91 code, which was chosen as it takes into account pre-equilibrium emissions. For non-\ensuremath{\alpha}-emitting channels, the experimentally measured excitation functions---after correcting them for possible contributions from higher charge isobaric precursor decays---were, in general, found to be in good agreement with theoretical predictions. However, for \ensuremath{\alpha}-emitting channels, the measured excitation functions had significantly more production cross sections than what pace4 predicted. This enhancement may be attributed to incomplete fusion processes. An attempt was made to estimate the incomplete fusion fraction in order to compare the relative importance of complete and incomplete fusion processes. The incomplete fusion fraction was found to be sensitive to the projectile energy and mass asymmetry of the entrance channel. We also discuss the results in terms of the impact of the frozen \ensuremath{\alpha}-cluster structure of the ${}^{12}$C isotope on various fusion reactions.