12C(6Li, d)16O and16O(6Li, d)20Ne at E(6Li) = 42 MeV

Abstract

Spectra up to 25 MeV excitation in 16O have been obtained from 12C(6Li, d) at 42 MeV bombarding energy. Angular distributions have been measured for ten states, including two J[pi] = 1- states of astrophysical interest, and appear to be mostly direct [alpha]-transfer. In addition, data for 16(6Li, d)20Ne(g.s.) and 20Ne*(2+) have been obtained. Excitation energies and widths have been extracted for states in 16O, including several states at Ex > 15 MeV. Alpha spectroscopic factors, S[alpha], and reduced [alpha]-widths, [gamma]2[alpha] and [theta]2[alpha] have been deduced for levels in 16O and 20Ne and compared with theoretical predictions. The J[pi] = 1- levels in 16O at 7.12 and 9.6 MeV excitation appear to have comparable S[alpha] and [gamma]2[alpha] values, viz. [gamma]2[alpha] (7.12 MeV)/[gamma]2[alpha] (9.6 MeV) = 0.6+1.7-0.3. Both states have apparent S[alpha] and [gamma]2[alpha] values smaller than that for the J[pi] = 2+ "[alpha]-cluster" state at 6.9 MeV however. Furthermore, the observed line shape for the J[alpha] = 1-, 9.6 MeV level indicates [Gamma]c.m. = 400 +/- 50 keV, which is substantially less than the accepted width for this level [Gamma]c.m. = 510+/-60 keV). The possible implications of these results for stellar helium burning calculations are discussed.