Closed-loop intracavity photoacoustic overtone spectroscopy

A technique is described whereby photoacoustic spectra of sample gases may be taken without the need for subsequent calibration of the wavelength scale. Laser power is measured externally with a pyroelectric detector, rather than internally with a silicon photodiode. Previously observed étaloning effects are dramatically reduced. Recent improvements in photoacoustic cell design by Zare et al. are employed. The technique is demonstrated by measuring the fifth CH stretching overtone spectrum of diethyl ether. © 1992.