TABLE OF CONTENTS One-nucleon transfer reactions probe the single-particle structure of nuclear states. The angular distribution is sensitive to the orbital angular momentum of the state into which the nucleon is transferred. The magnitude of the cross section determines the spectroscopic factor, which measures the degree to which the nuclear state is a pure single-particle state. For two-nucleon transfer reactions, the angular distribution again is sensitive to the angular momentum transferred in the reaction. This must always be so when the direct single-step transition dominates a reaction, according to the general arguments given in Chapter 2. It is a reflection of the conservation of angular momentum. However, here the angular momentum is carried by a pair of nucleons, so that it does not directly reflect the angular momentum of the single-particle states into which the nucleons are transferred. Only to the extent that the two single-particle angular momenta must sum to the transferred angular momentum is there a constraint. Obviously, the angular momentum of the pair generally can be shared between them in many different ways, and nothing in the measurement of the transferred angular momentum distinguishes between these. Therefore, all such ways that the angular momentum can be shared, consistent with the structure of the nuclear states connected by the reaction, must contribute coherently to the reaction. This coherence can produce large cross sections in states for which it is constructive and very small ones in states for which it is destructive. The coherence...
