Theoretical framework of nucleon exchange reactions There has been a lot of interest in nucleon transfer reactions in the recent past. Is there any theoretical framework to understand this? I am hopefully looking for literature that could potentially point me to what has been done to understand one nucleon or two nucleon transfer reactions.
 A: Theory of nuclear reactions (at low energies - which is seemingly the question topic) have started in 30ties in the direction of compound nucleus reactions. This gave a lot of explanations and some questions until
S.T.Butler and others 
developed direct reaction theory (in 50ies). With the rise of the Shell Model (SM) of people around M.G.Meyer this appeared an interesting probe to investigate where the nucleons are located (within the S scheme). It is a broad theme. I would recommend:
N.K. Glendenning - Direct nuclear reactions 1983
D.Jackson - Nuclear reactions 1970
I.J.Thompson and F.M.Nunes - Nuclear reactions for astrophysics 2009
C.A.Bertulani - Nuclear physics in a nutshell - chapter 10 - 2007
The theory usually starts with plane wave scattering and goes through Green functions to optical potentials and DWBA method. If you start to understand the concepts, then you can get into the debates in different fields in nuclear physics, validity of spectroscopic factors, surrogate reactions, complete description of activation reactions...
Everything depends on what you mean by understanding.
