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