Atomic response to bichromatic crossed‐beam field

We treat the excitation‐fluorescence response of an atom to a bichromatic, crossed‐beam field, both in terms of a time‐dependent physical spectrum, and optical Bloch equations. Agreement is found between narrowband illumination for a broad velocity distribution, and broadband illumination in phase sensitive fluorimentary. For strong fields, essential features of the Rabi structure are shown to remain even if the velocity distribution exceeds the homogeneous linewidth. Advantages of a crossed‐beam experiment are pointed out.