Nonlocality of the isobar propagation and the effective. delta. -nucleus spin-orbit interaction

The imaginary central and spin-orbit components of the ..delta..-nucleus optical potential are investigated in a ..pi..-exchange model. It is found that the effective spin-orbit interaction of the isobar reflects large nonlocalities from true pion absorption and from the quasielastic ..delta.. decay. The parameters for the absorption and the spin-orbit strength are in qualitative agreement with recent phenomenological results.