12C( 6Li, d) 16O at E(Li) = 90 MeV

Abstract

The 12C( 6Li, d) 16O reaction has been studied at E( 6 Li) = 90.2 MeV with a magnetic spectrometer. Spectra up to E x ≈ 30 MeV in 16O have been obtained and decay line widths, Γ c.m., have been extracted for broad levels. Known α-cluster states ( J π = 2 +, E x = 6.9 MeV; J π = 4 +, E x = 10.35 MeV) are preferentially populated exhibit sharply forward peaked angular distributions in contrast with ( 6Li, d) data obtained at lower bombarding energies. These features are well reproduced by reaction calculations assuming direct alpha-particle transfer provided one utilizes realistic optical model, target, and projectile wave functions. Alpha spectroscopic factors and reduced alpha widths have been extracted for levels E x < 12 MeV including J π = 1 − levels of astrophysical interest. The results are compared with other recent measurements and theoretical calculations. There is generally at least qualitative agreement (within × 2) between the various experiments and theories. The analysis indicates a non-negligible alpha width for the J π = 1 − level at E x = 7.1 MeV in 16O (which determines the 12 C → 16 O stellar helium burning rate) with 0.3 < θ α 2 (7.1 MeV)/ θ α 2 (9.6MeV) < 0.6 and 0.1 < θ α 2 (7.1 MeV)/ θ α 2 (6.9 MeV) < 0.4.