Elimination of line-shape distortion in laser absorption spectroscopy in atomic beams.

Line shapes observed when direct laser absorption is used in an atomic beam of sodium show asymmetries not present in fluorescence detection. Such line-shape distortion, which can be explained by resonant light diffraction by the atoms in the atomic beam, may be eliminated by imaging the fields in the interaction region at the surface of a detector located outside the beam apparatus.

Precision atomic-beam studies of atom-field interactions.

We have performed a high-resolution study of the interaction of two monochromatic laser fields with a prepared three-level cascade system in an atomic beam of sodium. The pump laser was held fixed near resonance with the lower levels while the probe laser was tuned over the upper two levels. For weak fields we observed a probe line shape that agrees with theory and shows that the intermediate level does not contribute to the linewidth. Data taken with a strong pump field were in disagreement with theory, but this disagreement is removed when atomic recoil suffered during the interaction is included in the calculation.