Astrophysical production rates for Li, Be, and B isotopes from energetic H(1) and He(4) reactions with HeCNO nuclei

Abstract

Calculations for Li, Be, and B nucleosynthesis in reactions of energetic <SUP>1</SUP>H and <SUP>4</SUP>He nuclei with <SUP>4</SUP>He, <SUP>12,13</SUP>C, <SUP>14</SUP>N, and <SUP>16</SUP>O nuclei have been performed. The calculations employed a recent compilation of cross section systematics for these reactions. Specific models examined include galactic cosmic-ray interactions with the interstellar medium, synthesis in flares, and formation in shock waves. The GCR + ISM calculations are able to account for the absolute abundances of <SUP>6</SUP>Li, <SUP>9</SUP>Be, <SUP>10</SUP>B, and <SUP>11</SUP>B satisfactorily, but require a low-energy component of spectral form E<SUP>-γ</SUP> to account for the <SUP>11</SUP>B/<SUP>10</SUP>B isotopic ratio, where γ = 5-7. In these calculations <SUP>7</SUP>Li is underproduced by an order of magnitude. The required <SUP>7</SUP>Li is most probably provided by the big bang, an assumption that is consistent with an open universe. Synthesis solely in a flare mechanism cannot reproduce the observed relative abundances. The shock wave mechanism can account for the relative abundances, but only in a very narrow energy window near E/A = 10 MeV.