Yu.A. Kuritsyn

Dynamic range improvement and background correction in diode laser atomic absorption spectrometry

The peculiarities of background correction and linearization of a calibration curve in atomic absorption spectrome- try with semiconductor diode lasers have been investigated. The logarithmic conversion of a signal was shown to be a very efficient tool for signal processing. The linearity of the calibration curve up to a concentration nearly three . orders of magnitude above the characteristic concentration absorbance 1.7 was obtained. Background absorbances up to 1.4 did not influence the value of the analytical signal in a graphite furnace, nor did it cause a significant increase in the noise. An absorbance of 4 = 10 y5 could be measured with a background absorbance of 1.2. Q 1999 Elsevier Science B.V. All rights reserved.

Development of Diode Laser Absorption Spectroscopy Method for Determining Temperature and Concentration of Molecules in Remote Object

We develop a method of diode laser absorption spectroscopy for noncontact measurements of the temperature and pressure of a gas mixture under unsteady-state conditions at low signal-to-noise ratios. The method is based on the measurement of the absorption spectra of water molecules and approximation of experimental spectra by spectra simulated based on spectroscopic databases. Different approximation algorithms of experimental spectra are tested, such as fitting by individual contours and fitting by a part of the simulated spectrum. We reveal that, at small signal-to-noise ratios, the approximation of experimental data by a simulated spectrum yields more correct data on the temperature of the mixture compared to the fitting by individual contours. For the examined temperature range of 300–1300 K, the determination error of the gas temperature in the test cell proved to be approximately three times lower than upon fitting by individual contours. The developed method of recording and processing spectra is used to measure the temperature, water vapor concentration, and total pressure under the unsteady-state combustion conditions of an air-hydrogen mixture in a supersonic flow.

Study of the v 2 infrared band of GeH4: Q-branch

The results of recording of the diode-laser spectrum of GeH4, having a natural distribution of isotopes, within the range 932·4-937·5 cm-1 are presented. Taking into account the Coriolis interaction between (0100) and (0001) vibrational states, the rotational and centrifugal constants are obtained.

Measurement of Non-Stationary Gas Flow Parameters Using Diode Laser Absorption Spectroscopy at High Temperatures and Pressures

The layout of an absorption spectrometer with diode lasers for contactless measurement of the temperature and water-vapor concentration in gas flows with mixture pressures of up to 3 atm and temperatures of 300–2000 K has been designed. The technique is based on the rapid tuning of the radiation wavelength of two lasers, the registration of the absorption lines of water molecules that are located in the tuning range, and the fitting of the experimental absorption spectra by theoretical ones that have been simulated using spectroscopic databases. The original components of the spectrometer and different algorithms of the processing of experimental spectra are described. The performance of the spectrometer and processing methods were tested in the laboratory with a cuvette at a pressure of 1 atm and temperatures of 300–1500 K. The different processing algorithms give a reasonable coincidence of data on hot zone parameters that were obtained by the method of diode laser absorption spectrometry, and the temperature that was measured using standard sensors. The designed layout of the spectrometer passed the first tests on the T-131 experimental stand at the TsAGI (Central Aerohydrodynamics Institute).

Determination of the Parameters of Condensed Media by the Dual-Wavelength Differential Absorption Method

A method of dual-wavelength differential absorption with the use of diode lasers is proposed. The method makes it possible to detect changes in parameters of media that cause broad absorption lines of selected molecular components of these media either to shift or to deform. The potentialities of the method proposed are demonstrated in experiments on remote contactless measurement of the temperature of aqueous solutions and measurement of the deviations of the composition of a mixture of dyes from the equilibrium state. These investigations show ways of increasing the sensitivity of the method proposed in solving particular experimental tasks.