Barrier distributions of the Mg 24 + Zr 90,92 systems: Influence of energy dissipation

We present results of barrier distribution measurements for Mg24+Zr90,92 systems by the backscattering method. The measurements were done at near-barrier beam energies of 68-88.5 MeV (in the laboratory frame) at six angles. A strong discrepancy between experimental results and the predictions of the standard coupled channels calculations was observed. To test the hypothesis that this discrepancy may be due to partial energy dissipation caused by coupling to many target noncollective levels, we performed calculations using the coupled channels plus random matrix theory (CC+RMT) model. The comparison of calculations with experimental results gives qualitative support of the hypothesis; however, quantitatively the agreement is not as good as in the case of the Ne20 projectile.