| Models of the r-process are extremely sensitive to the rate of production of 9Be, because the alpha(alpha n, gamma) 9Be reaction is the primary mechanism for bridging the unstable mass gaps at A=5 and A=8 in explosive environments that are rich in neutrons. A sequential two body process of alpha + alpha + n → 9Be is the primary channel for synthesis of 9Be. It is impossible to measure this reaction sequence in a laboratory, because no appreciable amount of 8Be (taulifetime = 10-16 s) could ever be produced, and then subsequently bombarded with neutrons. However, the 8Be(n, gamma)9Be cross-section may be deduced from the 9Be(gamma,n)8Be cross-section using the reciprocity theorem. This thesis reports on a new measurement of the 9Be(gamma,n)8Be reaction cross section with an unprecedented accuracy, and a precision of +/- 4.6%. From these new measurements, the astrophysical alpha(alpha n, gamma) 9Be reaction rate has been determined with similar accuracy and precision. This new rate will give insights into the conditions necessary for the r-process to occur in explosive environments like Type II supernovae. |
