Dirac theory of nucleon-nucleus collective excitation

We obtain the relativistic distorted wave impulse approximation amplitude for nucleon-nucleus collective transitions using an eikonal formalism. The effect of the Darwin term is to suppress the upper-to-upper contribution and enhance the lower-to-lower compared with a nonrelativistic treatment. In collective transitions these combine in a way that results in a transition density proportional to the derivative of the total Dirac distortion including quadratic and spin-orbit pieces. This leads to the same phenomenologically successful relations between elastic and inelastic amplitudes as in the Schroedinger description for collective transitions and promises a better treatment of noncollective transitions. We comment on the vanishing of P-A in this treatment