Influence of collision processes on saturated absorption line shapes

The effect of collision processes especially of velocity-changing collisions on the shape and contrast of the absorption dips is examined considering the dynamical Stark effect. The velocity-changing collisions cause a homogeneous saturation of the Doppler-broadened absorption profile and a decrease of the contrast of the absorption dip, which is comparable with the decrease of the contrast due to the dynamical Stark effect for saturation intensities of the order σI?1. The influence of the dynamical Stark effect decreases with increasing pressure whereas the influence of the homogeneous saturation increases.