  We continue the study of scattering theory for the system consisting of a
Schr"odinger equation and a wave equation with a Yukawa type coupling in space
dimension 3. In previous papers, we proved the existence of modified wave
operators for that system with no size restriction on the data and we
determined the asymptotic behaviour in time of the solutions in the range of
the wave operators, first under a support condition on the Schr"odinger
asymptotic state and then without that condition, but for solutions of
relatively low regularity. Here we extend the latter result to the case of more
regular solutions.
