Oscillations in the angular distributions of heavy-ion transfer reactions

Oscillations in the angular distributions are established as a general feature of heavy-ion induced, few-nucleon transfer reactions at incident energies sufficiently above the Coulomb barrier. For proper Q-matching with incident and exiting energies well above the Coulomb barrier, the angular position of the most forward maxima in the differential cross section is characteristic of the transferred angular momentum. The threshold for such oscillations is particularly sensitive to the absorptive potential near the nuclear surface requiring potentials that are strongly absorbing in the nuclear interior but nearly transparent at the surface. Evidence also is presented for an energy dependent surface absorption. Certain anomalous cases where the oscillating cross sections are predicted to be out of phase with the data are discussed. (orig.)