Abstract

The line shapes in intermodulated optoacoustic spectroscopy are experimentally investigated by a laser-Stark technique. A stabilized CO₂ laser is used to study some infrared transitions of NH₃ under different conditions of gas pressure and laser power. In the presence of strong saturation the experimental line shapes are appreciably different from simple Lorentzian curves. We prove that the main reason for this distortion is the inhomogeneous saturation caused by the Gaussian profile of the beam intensity. Similar effects are also indicated in Doppler-limited spectra by an additional power-dependent broadening and are explained by a same model. At strong saturation, a line distortion of this type may also be present in conventional and nonconventional detection methods of high-resolution spectroscopy.

© 1986 Optical Society of America

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