The elastic scattering of ${}^9\mathrm{Li}{+}^{12}\mathrm{C}$ and ${}^{11}\mathrm{Li}{+}^{12}\mathrm{C}$ has been measured at an incident energy of 50 MeV per nucleon over the angular range from 2° to 15° in the center-of-momentum frame. The elastic and inelastic reaction channels were cleanly separated in the critical forward-angle region where a predicted nearside/far-side interference minimum should be observed. The angular distributions obtained in this experiment are consistent with existing quasielastic measurements at 60 MeV per nucleon. In particular, the ${}^9\mathrm{Li}$ data display the interference minimum, while it is absent for ${}^{11}\mathrm{Li}.$ This difference is shown to occur in the elastic channel, and the results are discussed in terms of strongly enhanced surface refraction in the ${}^{11}\mathrm{Li}$ case.

• Received 12 October 2002

DOI:https://doi.org/10.1103/PhysRevC.67.014601