Validity of scaling property and iso-centrifugal approximation in quasielastic barrier distribution: the first experimental verification

Abstract

For the first time, we have simultaneously measured fusion and quasielastic excitation functions for an intermediate mass system for angular momentum, \(\ell \sim 0\) using a recoil mass spectrometer. We have extracted barrier distributions using three different sets of data recorded simultaneously for the reaction \(^{16}\)O+\(^{142}\)Ce: (a) fusion excitation function from measurement of evaporation residues at angle, \(\theta _{\text {lab}} = 0^{\circ }\), (b) quasielastic excitation function at center of mass scattering angle, \(\theta _{\text {c.m.}} = \pi \) via measurement of scattered target-like ions at \(\theta _{\text {lab}} = 0^{\circ }\) and (c) quasielastic excitation functions from measurement of scattered projectile-like ions at two large angles. We show that the four barrier distributions yield nearly identical results with a single peak. However, the centroids of the barriers extracted from quasielastic data at large angles are lower by \(\sim 600\) keV compared to the same of the barriers extracted from fusion and quasielastic data for \(\ell \sim 0\). This is the first experimental verification of the validity of scaling property with respect to \(\ell \) and iso-centrifugal approximation in extracting fusion barrier distribution from quasielastic scattering. This work also points to the importance of extracting barrier distribution from quasielastic measurements at \(\theta _{\mathrm {c.m.}} = \pi \) for systems for which measuring fusion excitation function with high precision is not feasible.