Speaker
Prof.
Claudio Spitaleri
Description
In the last decades, impressive improvements in astronomical observations and in computational models of stellar structure and evolution have made it possible for the first time to significantly improve our understanding of energy generation and nucleosynthesis processes that take place in a variety of astrophysical sites.
Nuclear reactions in such environments remain a key ingredient for the detailed description of stellar evolution and for the explanation of the abundance of the elements in the Universe. Ideally, laboratory measurements of key astrophysical reactions should be carried out at the energy of astrophysical interest, referred to as the Gamow energy region, which depends on the temperature of the stellar plasma at which a given reaction takes place as well as on the charges of the interacting nuclei [1].
For charged-particle induced reactions the cross section E) drops exponentially with decreasing centre-of-mass energy due to the hindrance of the Coulomb barrier. As a consequence, experimental measurements become increasingly more challenging and extrapolations from data at higher energies are needed
So far, only a few reactions have been studied at the relevant Gamow energy region. In all other cases, extrapolations of reaction cross sections are carried out from data taken at higher energies. Secondly, the measured cross sections must be corrected for the effect of electron screening [2,3] arising from the presence of electrons in the target atoms and, possibly, in the (partly)-ionised projectiles.
Because of these intrinsic limitations in the direct experimental study of nuclear reactions for astrophysics, alternative methods for determining bare-nuclei cross sections are needed. In particular, the THM has proved to be an extremely useful and versatile approach to extract nuclear reactions of astrophysical relevance which turns out to be insensitive to the screening effect and allows to determine the energy dependence of the reaction cross section in the region of astrophysical interest. The key ideas on which the method is based and the the recepy to extract data are presented .
[1] C.E.Rolfs and W.S.Rodney, Cauldrons in the Cosmos, University of Chicago Press, Chicago, 1988
[2] H.J.Assembaum, K.Langanke and C.Rolfs, Z. Phys. A327, 461 (1987)
[3] F.Strieder, C.Rolfs, C.Spitaleri, and P.Corvisiero, Naturwissenschaften 88, 461 (2001)
