Influence of laser intensity on absorption line broadening in laser absorption spectroscopy

Abstract

The influence of laser intensity on absorption line broadening was investigated. Laser absorption spectroscopy was applied to low-pressure plasma, and the translational temperature deduced from the Doppler width was found to increase with laser intensity; this was in contrast to the conventional laser theory. Consequently, the dependency of absorption saturation on the Doppler frequency was considered. The predicted variation in broadening width with laser intensity showed a good agreement with the measurement. In addition, we obtained a correction factor for the temperature measurement at high laser intensity.

Diode-Laser Induced Fluorescence Spectroscopy of an Optically Thick Plasma in Combination with Laser Absorption Spectroscopy

“…By fitting the measured with (6), and are obtainable. According to an earlier report [11], the true Doppler broadening is obtainable when the saturation parameter, (= / ), is less than 0.1. With a ratio of saturated broadening to the true Doppler broadening, the saturation effect is corrected.…”

“…In DLIF, however, the laser spectral width is about 1 MHz and three others of magnitude narrower than the absorption profile broadening. The mechanism of broadening differs, but with identical broadening to that of LAS [11][12][13].…”

On-line spectroscopic and spectrometric methods for the determination of metal species in industrial processes☆

“…At the high pressures and temperatures of many industrial processes, absorption lines of the species to be detected are usually severely broadened and shifted as a result of collisions with molecules in the measurement volume [219,220,224,225]. Typical spectral linewidths (FWHM) at 1 bar are 3e6 GHz and at 10 bar 30e60 GHz, compared to only about 1e2 GHz at 1 mbar.…”

Pressure broadening of Ar and Kr (n+1)s[3/2]2→(n+1)p[5/2]3 transition in the parent gases and in He

“…The authors of [4] tried to assess it using an empirical formula for temperature in the gas discharge cell. Also, laser intensity of $ 0.1 mW mm À 2 in their experiments was quite high and might influence the absorption line profile [6]. Nevertheless, in their times they managed to obtain the values for the pressure broadening coefficient quite close to measured by a fare more sophisticated method [7].…”