Charge transfer in helium in a laser field. II. Nonlinearity and photon correlation effects

We have extended an earlier study of the effect of a laser field on He+-He charge-transfer collisions to consider the effect of a finite laser bandwidth and to include the full multiple-photon exchange with the field. The first effect is shown to be negligible so long as the collision time lies within approx.h/(bandwidth). As regards the second aspect, we show that in this nonperturbative treatment it can only be studied by discarding the rotating-wave approximation. Charge-transfer cross section after photon exchanges with the field until ''saturation'' is found to have a nonlinear, oscillatory intensity dependence