The time-dependent theory of Courtens and Sz\"oke is generalized using the approach of Burnett et al. to derive time-dependent spectral intensities of resonance fluorescence from atoms driven by a pulsed laser in the presence of collisions. These results are valid both for laser detunings inside and outside the usual impact region of the spectrum, including Zeeman degeneracy effects. We apply this theory to a simple but important example ($J=0$ to $J=1$) to obtain quantitative predictions for the observable scattered-light spectrum which can be directly compared with recent experiments.

We extend the theory of light scattering from an atom undergoing collisions to the case of strong laser fields, where the expansion in powers of $\ensuremath{\Omega}{\ensuremath{\tau}}_{c}$ that was used formerly in a series of papers by Burnett et al. breaks down. In particular we consider in detail the conditions necessary to relate the observable quantities to intense-field collisional rate constants in a dressed-state basis (such as those calculated by Light and Sz\"oke). We also show (following Rabin and Ben-Reuven) that by studying the spectrum emitted by the atoms in the presence of a strong field one may measure the collisional rates for transfer between the dressed states of atom plus radiation field.

We describe our observations of the effect of stimulated and four-wave mixing processes on the kinetics of atomic states dressed by an intense laser field in the presence of collisions. The effects are observed via the forward- and side-scattered light. We suggest that the effects observed by Harter et al. are produced by amplification of background laser fluorescence by these processes.

We report observation of the scattered spectrum from a Zeeman degenerate atom at high laser intensities. For a J = 0 to J = 1 transition in the presence of collisions we observe an asymmetric triplet in the polarization parallel to the incident laser and an asymmetric doublet in the polarization perpendicular to the incident laser.

The qualitative form of the predictions of Light and Szoeke for an optical collision involving the lambda460.7-nm transition in strontium perturbed by argon has been verified. In the presence of a linearly polarized laser the m/sub J/ = 0 to m/sub J/ = 0 is ''switched off'' at large field intensities (> or approx. =50 MW/cm/sup 2/) whereas the m/sub J/ = 0 to m/sub J/ = +- 1 transition is not observed to saturate. The consequences for the study of laser-induced phenomena is discussed.