Dissociation ofLi6

Interactions of ${\mathrm{Li}}^6$ ions with carbon and nickel targets have been investigated at incident ${\mathrm{Li}}^6$ energies of 36 and 63 MeV, utilizing a $\left(\frac{\mathrm{dE}}{\mathrm{dx}}\right)\times E$ product identification system capable of separating individual product isotopes. Contrary to expectations based on previous studies in this laboratory on the ${\mathrm{Li}}^6({\mathrm{Li}}^6, d){\mathrm{B}}^{10}$ reaction at 6 MeV which demonstrated a direct reaction mechanism involving the transfer of an alpha particle, no evidence was obtained in the experiments reported herein for deuteron groups corresponding to population of isolated residual states. Each deuteron energy spectrum exhibited a single broad peak, centered at an energy corresponding to the beam velocity, indicating that a direct dissociation mechanism dominates lithium interactions at these higher energies, thus precluding use of ${\mathrm{Li}}^6$ ions at high energies as nuclear spectroscopic probes. The total dissociation cross section for 63-MeV ${\mathrm{Li}}^6$ ions on carbon, for example, was found to be 24% of the total geometric cross section. In order to establish whether the ${\mathrm{Li}}^6$ dissociation proceeds sequentially through well-defined excited states, the elastic and inelastic scattering both of a ${\mathrm{C}}^{12}$ beam from a ${\mathrm{Li}}^6$ target, and of a ${\mathrm{Li}}^6$ beam from a carbon target, were studied. These data demonstrate that processes wherein binary dissociation follows inelastic excitation of unbound ${\mathrm{Li}}^6$ states can account for less than 5% of the observed events. It is concluded that the dissociation mechanism is a direct one, reflecting strong alpha-particle plus deuteron-cluster amplitudes in the ${\mathrm{Li}}^6$ wave function. Analysis of the dissociation product angular distributions suggests that the dominant interaction involved in these studies is nuclear scattering of the center of mass of the ${\mathrm{Li}}^6$ ion from the target. Preliminary studies on the dissociation of ${\mathrm{Li}}^7$ and of ${\mathrm{B}}^{10}$ and ${\mathrm{B}}^{11}$ have also been carried out; in each case, an alpha particle is again a dominant dissociation product.