2-NEUTRON CAPTURE REACTIONS IN SUPERNOVAE NEUTRINO BUBBLES

Recent calculations suggest that the neutrino heated bubbles in the po stcollapse phase of type II supernovae may be the site of the r proces s. The nucleosynthesis process depends on the expansion and cooling ra tes as well as on the rates of the alpha-particle and neutron recombin ation processes that bridge the mass gaps at A = 5 and 8. We have reex amined the rate for the important reaction He-4(alpha n,gamma) Be-9, a nd estimated the rates for the two neutron capture reactions on He-6 a nd He-8 which could provide an alternative reaction path. We find that the most important reaction for initiating the cu process is the He-4 (alpha n,gamma) Be-9 reaction, as suggested by earlier work.