DOPPLER-FREE OPTOACOUSTIC SPECTROSCOPY

The first observation of Doppler-free optoacoustic spectroscopy is reported. As a first example the P (193) line of the 11-0 band of the B←X transition of 127I2 is used. The output of cw single mode dye laser is split into two equal intensity beams chopped at frequencies ω1 and ω2. The nonlinear compoment of the optoacoustic signal at the frequency (ω1 + ω2) is detected and Doppler-free resolution is obtained. Comparing the Doppler-free optoacoustic and fluorescence spectra of iodine measured under similar conditions, good agreement is found. Since optoacoustic and fluorescence methods complement each other, this opens up new possibilities for weakly or nonfluorescing molecules. © 1979.