Comment on fusion cross sections in the⁴⁰Ar+⁴⁰Ca and⁴⁰Ca+⁴⁰Ca systems

Abstract

Cross sections for the production of evaporation residues in a fusion reaction have been extracted from measurements of cross sections for elastic, quasi-elastic and deep inelastic scattering of⁴⁰Ar projectiles on⁴⁰Ca target nuclei at incident energies E_LAB=191, 236 and 272 MeV. The extracted data are compared with the predictions of a one-body window-friction model including a neck configuration in the interaction phase between the projectile and target nuclei. Furthermore, the results for the⁴⁰Ar+⁴⁰Ca system are compared to those obtained in the similarly mass-symmetric system⁴⁰Ca+⁴⁰Ca where directly measured evaporation residue data are available.

The fusion reaction in heavy ion collisions has so far been studied mostly at low incident energies and for systems where the fusion cross section is in good approximation given by the cross section for evaporation residues [1]. This approximation has been verified only for heavy interacting systems (A> 100 for the combined system). In this paper we comment on the problems of fusion cross sections for the lighter projectile-target combination⁴⁰Ar+⁴⁰a and give evidence that this approximation may not be generally valid.