The ({sup 8}Li, {alpha}) reaction at low energy: Direct {sup 4}H cluster transfer?

The ({sup 8}Li, {alpha}) reaction has been studied at E({sup 8}Li)=27.7 MeV on targets of {sup nat}C, {sup 27}Al, and {sup 208}Pb using a secondary {sup 8}Li beam. The {alpha}-energy spectra for {sup 27}Al and {sup 208}Pb are generally nondistinct and resemble fragmentation spectra. In contrast, data for the {sup nat}C target exhibit enhanced ({sup 8}Li, {alpha}) cross sections in the region corresponding to population of low-lying levels in {sup 16}N. Angular distributions were determined over a large angular range and exhibit a strong forward peaking for {sup 27}Al and some forward peaking for the {sup nat}C data. They are otherwise rather featureless but distinct from spectra expected from fusion evaporation. The data for {sup 27}Al are indicative of either direct or sequential fragmentation processes. Similar analysis of limited data obtained at E({sup 8}Li)=27.7 MeV for the {sup 208}Pb target, along with data previously obtained at higher {sup 8}Li energies, is suggestive of a sequential breakup mechanism. In the case of the {sup nat}C target, the data corresponding to low excitation energies in {sup 16}N exhibit ({sup 8}Li, {alpha}) angular distributions that appear to be most consistent with a {sup 4}H transfer mechanism. However, we cannot distinguish between a one-stepmore » {sup 4}H cluster transfer and a multistep {sup 4}H transfer (such as n + {sup 3}H)« less