Opto-acoustic spectroscopy employing amplitude and wavelength modulation

Abstract

An intense light source, preferably of high monochromaticity, having its beam modulated at a frequency f.sub.o through a wavelength range including an absorption line of a species to be detected, energizes a chamber containing a sample of the species. The modulation frequency may also be a multiple or sub-multiple of the natural resonant accoustic frequency of the sample chamber. A microphone in the sample chamber provides an output signal proportional to the concentration of the species. The radiation beam is further incident upon a calibration chamber containing a predetermined concentration of the species. A microphone in the calibration chamber provides a calibration signal for comparison with the sample signal to determine the concentration of the species in the sample cell. Means are provided for adjusting the center of the wavelength modulation range so that it bears a known relation to the center of the species absorption line.

Dependencies are inferred from the claim text.