Direct reaction theories for exotic nuclei: An introduction via semi-classical methods

The structure of exotic nuclei has only been studied from around 1985, because they are very short lived and because before that, it was not possible to produce and deliver them as beams on a target. They have large N∕Z or Z∕N ratios, are weakly bound and quite extended most of the time. Thus breakup, transfer and/or inelastic excitations of the surface are some of their most common reaction mechanisms. Direct reactions, for their simplicity, have played a fundamental role in the last thirty years in the process of understanding such “new” type of structures. On the other hand, direct reactions have been studied and understood for a much longer time, starting with the pioneering experiments in the early '50 on deuteron-induced reactions and the reaction models developed by S.T. Butler and collaborators. Both subjects are extremely vast and there is a large literature available of books, review articles and original papers. I will discuss here only a few selected examples of the many interesting problems that have been encountered and solved in all those years. I consider them breakthroughs in the field and as such I hope they can inspire young generations of researchers.