COMPOUND NUCLEUS FORMATION IN NITROGEN–OXYGEN AND OXYGEN–OXYGEN REACTIONS

The experimental cross section for the reaction O16(N14,2p)Al28 is compared with the predictions of the square-well model of compound nucleus formation over the range 6.3 to 12 Mev (center of mass energy). The branching ratio is estimated from the experimental cross section for the comparison reaction Si29(p,2p)Al28 over the same range of excitation in the compound nucleus P30*. It is found that the branching ratio probably increases from about 10% to 20%, which requires the nuclear interaction radius for N14 + O16 to decrease from about 8.5 to 7.5 fermis as the energy is increased over this range.Because of the similarity in mass and observed charge distributions in N14 and O16, the interaction radius for compound nucleus formation in a collision between two oxygen nuclei is probably also similar and in the range 8.0 to 9.1 fermis at energies far below the Coulomb barrier. A consequence of this result is that oxygen ions, which may be present in the cores of sufficiently developed red giant stars, will be destroyed by O16 + O16 collisions in about 105 years and 1 year respectively, at temperatures in the vicinity of 13.0 and 18.5 × 108 °K.