Speaker
Description
In stellar evolution, the rate of $ ^{12}$C($ \alpha$,$ \gamma$)$ ^{16}$O reaction controls the C/O abundance ratio at the end of the helium burning phase, thus defining the further course of development. At stellar temperatures of around 300 keV, the cross section of $^{12}$C($\alpha$,$\gamma$)$^{16}$O is $\sim$ 10$^{-17}$ b, which cannot be measured using current technology. The $\alpha-$capture reaction populating the natural-parity states of the residual nuclei, is an effective indirect tool for studying these types of reactions. In this case, it corresponds to the alpha pickup by $^{12}$C to populate states of $^{16}$O, predominantly the 6.917 MeV state. Loosely bound stable nuclei with prominent $\alpha-$cluster structure, such as $^{6,7}$Li, $^{11}$B have also been used in such studies provided that these are "direct" $\alpha-$transfer and do not proceed via a compound nucleus. However, the breakup contributions from such nuclei have a significant impact on the transfer channels. Interestingly, the $^7$Be nucleus, though having an $\alpha-$cluster structure and a lower breakup threshold of 1.58 MeV, demonstrates lower breakup contribution compared to transfer cross section. In this context, we carried out an experiment at HIE-ISOLDE, CERN, with $^7$Be + $^{12}$C at E = 5 MeV/A to study $\alpha-$transfer reactions populating states in $^{16}$O, that dominantly contribute to the He-burning process. Preliminary results would be presented.
