Correlation spectral analysis of a halogen mixture by laser radiation with synthesized spectrum

Abstract

A laser with synthesized radiation spectrum is used for creating spectral masks for correlation analysis of a mixture containing molecular iodine and bromine. The choice of the wavelengths of spectral masks is substantiated, the accuracy and sensitivity to the presence of interfering substance are studied, and the influence of the mask instability is discussed.Spectroscopic methods based on tunable lasers are widely used in almost all science and engineering fields. A new type of tunable lasers, sweep lasers, whose dynamics was studied in the key works [3][4][5] by Ya. I. Khanin in the field, significantly contributed to the development of these methods [1,2]. The progress in these techniques and the related method of slitless laser spectrometry [6] is mainly due to the solution of the problem of all-electronic tuning of dispersion cavities, which made it possible to program the law of tuning, to improve its rate and accuracy, and to ensure reproducibility of tuning to the specified wavelength [7,8].The brand new method is related to the electronic tuning of the multifrequency oscillation spectrum, which opened up the way for artificial synthesis of radiation spectra with specified structure. This, in turn, contributed to the further development of the method of correlation frequency spectroscopy based on the correlation between the structure of the probing radiation spectrum and the structure of the absorption (reflection, amplification) spectrum of the studied material [8,9].The usefulness of measuring the absorption simultaneously at several wavelengths was reliably demonstrated in the method of correlation mask-spectrometry [10]. One mask transmits light in the maxima of the absorption spectrum, and the other mask, in its minima. In such cases, the difference between the corresponding readouts of the device is the measure of the amount of studied material, which is used for determining its concentration. Compared with other methods of gas analysis, this method allows one to significantly improve the signal-to-noise ratio for mixtures with overlapping absorption spectra.Within the framework of our approach, the spectral masks are created and changed by using a laser with electronic synthesis and tuning of the multifrequency spectrum [11][12][13]. The studies performed for the dye lasers show the possibility of stable generation of several spectral components whose wavelengths can be independently tuned by 8-10 nm. The masks with an arbitrary large number of components can be realized in the regime of the programmed tuning when the components are generated in succession. Such masks allow us to monitor several materials simultaneously, which is especially useful for analyzing mixtures with the time-varying composition.In this paper, we study the possibility of using the correlation methods for analyzing gas mixtures containing molecular iodine and bromine. The practical need in this method is related to the fact that the absorption spectra of these materials, which often accompany each other in various natural a...