The Spallagenic Production Rates of Lithium, Beryllium and Boron

Abstract

We calculate the production rates of Li6, Li7, Be9, B10 and B11 via spallation of Carbon, Nitrogen and Oxygen nuclei by protons and alpha-particles and by alpha-alpha fusion reactions. We include recent measurements of the cross sections of alpha-alpha fusion reactions and find that the computations yield rates of Li6 and Li7 production that are nearly a factor of two smaller than previously calculated. We begin by using the `straight ahead' approximation for the fragment energy and the `leaky-box' model for product capture in the Galaxy. In addition we test the straight ahead approximation by recalculating the production rates using an empirical description of the fragment energy distribution and find that the results closely match. We have also calculated the rates for various cosmic ray spectra and find that the hardest spectra tested decrease the rates with CR CNO by approximately an order of magnitude relative to our chosen standard. Finally we have computed the Population I elemental ratios and the Population II scaling relations for our standard and find that our computations predict an abundance of Lithium for a given abundance of Beryllium that is 1/4 smaller than previously derived.