The 12C(a,?)16O Cross Section at Stellar Energies

Abstract

An earlier calculation of the El contribution to the 12C(a, y) 160 cross section at stellar energies, which used R-matrix formulae with parameters chosen to fit 12C+ a phase shifts and the a spectrum from 16N {3 decay, is updated by including in the fit 12C(a, y) 160 cross section data. The E2 contribution is obtained by an R-matrix fit to 12C + a phase shifts and to data derived from 12C(a, y) 160 angular distribution measurements. Estimates of these contributions by others are discussed critically. It is suggested that the long-accepted value of the stellar cross section should be increased by a factor of about 2 rather than the factor 3-5 that has been proposed recently.