Spatially resolved saturated absorption spectroscopy in flames

This Letter describes the extension of saturated absorption spectroscopy to spatially resolved (point) absorption measurements for diagnostic applications. The technique modifies the standard configuration of Doppler-free saturation spectroscopy by using crossed, rather than counterpropagating, saturating and probe beams. The method is demonstrated in a study of the distribution of atomic sodium aspirated from a salt solution into an atmospheric-pressure hydrogen-air flame. Similar adaptations of other two-beam Doppler-free spectroscopic methods can be used to provide spatially resolved measurement techniques.