I have 2 questions... I was told that the transmutation of Li-7 to Be-8 by proton collisions at energies below the classical barrier verifies the QM description of the weak interaction cross section. Firstly, I found the leap in logic very confusing - does the weak force have a role in tunneling and fusion at all? I only knew that the weak interaction is at work in the deuteron formation step in the proton-proton chain and beta decay. I've been studying the subject only from Enge's Introduction to Nuclear Physics, which doesn't seem to help with my task. I need to figure what exactly is "the quantum mechanical description of reaction cross sections" for certain 1~2 MeV collisions... It seems to me that most introductory texts only briefly mention tunneling for collisions, and use a semi-classical description involving surmounting a Coulomb barrier, which you can say is the opposite of what I'm looking for. So, secondly, are there any texts one would recommend which are more relevant? And if the weak force is indeed implicated here, where can I start an understanding of the quantum description of the weak force? Thanks in advance!