The paper reports on experimental studies of the absorption of 13C16O2 in a mixture with 12C16O2 in exhaled air by laser absorption spectroscopy using a diode laser tunable in the frequency range 4860-4880 cm-1. The results of the studies showed that the minimum detectable concentration of 13C16O2 is at a level of less than 20 ppm, and this approach is promising for measuring the content of 13C16O2 in exhaled air for non-invasive online diagnosis of oncological diseases of the gastrointestinal tract at early stages

The paper reports on experimental studies of the absorption of 13 C 16 O 2 in a mixture with 12 C 16 O 2 in exhaled air by laser absorption spectroscopy using a diode laser tunable in the frequency range 4860-4880 cm -1 . The results of the studies showed that the minimum detectable concentration of 13 C 16 O 2 is at a level of less than 20 ppm, and this approach is promising for measuring the content of 13 C 16 O 2 in exhaled air for non-invasive online diagnosis of oncological diseases of the gastrointestinal tract at early stages. Keywords: diode laser spectroscopy, carbon dioxide, breath tests, oncological diseases of the gastrointestinal tract.

This paper presents the experimental measurement of hydrogen sulfide absorption coefficients in the pressure range of 75–460 mbar of two rotational absorption lines of the vibrational band of H 2 S molecule at 021-000 transition using the tunable diode laser absorption spectroscopy technique. The obtained results are compared with the data of the HITRAN spectroscopic database.

The paper reports on the calculation studies of the influence of the pressure of the analyzed gas mixture on the measuring sensitivity of the concentrations of 127 I 2 , 127 I 129 I and 129 I 2 in atmospheric air by the laser-fluorescence method using a copper vapor laser with a wavelength of 578.2 nm as a fluorescence excitation source. It is shown that for each of these iodine molecules there are pressures at which the highest fluorescence intensity is achieved, which correspond to the best detection sensitivity of the molecules. The results obtained can be used in the development of methods for real-time detection of molecular iodine in the atmosphere.

This paper reports on experimental measurement of H 2 S absorption in the spectral range of 4860–4880 cm −1 by means of diode laser absorption spectroscopy, and determines the H 2 S spectral absorption line in the generation area of the laser used, most promising in terms of H 2 S detection using this method.

A comparative analytical review of existing methods and means of measuring hydrogen sulfide content in gasses was performed. The method of infrared laser absorption spectroscopy, which uses semiconductor diode lasers tunable in the mid-infrared range as emission sources, is proving to be one of the most promising methods for solving these problems.

The experimental measurement of the R(18), R(20), R(22), R(24), R(26), R(28), R(30), R(34), R(36) absorption lines collision broadening for the 12C16O2 molecule vibrational band 20013–00001 and P(10), P(12), P(14), P(16), P(18), P(20), P(22) absorption lines for the 13C16O2 molecule 20012–00001 vibrational band have been reported in this paper. The research has been first carried out by the diode laser absorption spectroscopy method using a single-frequency diode laser emitting in the 4860–4880 cm−1 region. The dependences of the absorption constants and cross-sections of these lines on the 13C16O2 and 12C16O2 molecules mixture concentrations in the ratio of 1:140 have been studied. The obtained results have been compared with the HITRAN spectroscopic database data.

We report the experimental observation of the absorption constant values of (CO2)-C-12-O-16 and (CO2)-C-13-O-16 using the tunable diode laser absorption spectroscopy method ranging from 4860 to 4880 sm(-1) within the pressure limits of 8-240 mbar for the absorption curves (lines) R(18), R(20), R(22), R(24), R(26), R(28), R(30), R(32), R(34) and R(36) of the 20013-00001 molecule (CO2)-C-12-O-16 vibration band, and within the pressure limits of 0.06-1.7 mbar for the absorption curves P(10), P(12), P(14), P(16), P(18), P(20) and P(22) of the 20012-00001 molecule (CO2)-C-13-O-16 vibration band. In the work, as a mixture under analysis, a mixture of the isotopes (CO2)-C-13-O-16 and (CO2)-C-12-O-16 at the ratio of 1:140 was used. The results have been compared with the data of the HITRAN spectroscopic database.

The experimental measurement of the R(18), R(20), R(22), R(24), R(26), R(28), R(30), R(34), R(36) absorption lines collision broadening for the 12C16O2 molecule vibrational band 20013–00001 and P(10), P(12), P(14), P(16), P(18), P(20), P(22) absorption lines for the 13C16O2 molecule 20012–00001 vibrational band have been reported in this paper. The research has been first carried out by the diode laser absorption spectroscopy method using a single-frequency diode laser emitting in the 4860–4880 cm−1 region. The dependences of the absorption constants and cross-sections of these lines on the 13C16O2 and 12C16O2 molecules mixture concentrations in the ratio of 1:140 have been studied. The obtained results have been compared with the HITRAN spectroscopic database data.

This paper reports on the application of the Kalman method for processing the signal obtained by the tunable diode laser absorption spectroscopy method in an experimental circuit, which includes the frequency modulation of a diode laser pump current in combination with the synchronous detection technique. It has established that the implementing of this approach makes it possible to improve the measurement accuracy of the (CO2)-C-13 content, as well as the measurement accuracy of the (CO2)-C-13 and (CO2)-C-12 concentrations ratio in exhaled air to a level not exceeding 0.1%.

This paper reports on implementing the adaptive Wiener filtering algorithm for the processing of an experimental signal obtained by the tunable diode laser absorption spectroscopy technique near the wavelength of 2 mu m using a tunable diode laser. It has been shown that applying this filter may improve the (CO2)-C-13 content measuring accuracy in a mixture with( 12)CO(2) expiratory air.

The 1st, 2nd and 3rd order least square method (LSM-1, LSM-2 and LSM-3) is applied to smooth the experimental absorption signal of (CO2)-C-13 and (CO2)-C-12 obtained by the tuneable diode laser absorption spectroscopy method in the 4860-4880 cm(-1) frequency range of a tuneable diode laser. It has been shown clearly that using LSM-2 with a filter window N similar to 100 allows the (CO2)-C-13 content in exhaled air to be measured at an error level of 0.28%, which meets breathing tests requirements.

The use of adaptive Kalman and Wiener filters and the empirical mode decomposition algorithm for processing the experimental signal obtained by the tunable diode laser absorption spectroscopy method has been reported to improve the sensitivity of the measurement of (CO2)-C-13 content in human expiratory air. A laser diode, tunable in the range 4860-4880 cm(-1) near the wavelength of 2 mu m, is used as a source. It has shown that the application of these filters ensures a detection sensitivity of (CO2)-C-13 at the level of 10(15) cm(-3), while the minimum detectable fraction of (CO2)-C-13 in a mixture with the (CO2)-C-12 is 3.8.10(-5).

It has been shown clearly that using the synchronous detection technique with the pump current frequency modulation of a tunable diode laser emitting near 2 mu m wavelength, combined with the application of the Wiener filtering algorithm for the experimental signal, ensures a two-times improvement in the measurement accuracy for the (CO2)-C-13 content in exhaled air, and, for the (CO2)-C-13 and (CO2)-C-12 concentrations ratio, more than seven times.

This study reports on the use of Kalman’s method for filtering an experimental signal to improve the accuracy of a 13С16О2 measurement in the exhaled human breath using tunable diode laser absorption spectroscopy with a semiconductor diode laser tunable near to a wavelength of 2 µm. It is shown that Kalman’s filtration allows a 5-fold increase in the detection accuracy of 13СО2.

This paper develops the new selective real-time method of I-129(2), (II)-I-129-I-127, I-127(2) and NO2 detection in gases. Measuring concentrations of molecular iodine is based on fluorescence exciting by the radiation of a tunable diode laser, operating in the red spectral region (632-637 nm), at two or three wavelengths corresponding to the centers of the absorption lines of I-129(2), (II)-I-129-I-127 and I-127(2). Detection of NO2 is performed by measuring the intensity of the tunable diode laser radiation, which passed through the measuring cell. Measured simultaneously, boundary ratios of iodine molecule concentrations measured simultaneously are about 10(-6). The sensitivity of nitrogen dioxide detection is 10(16) cm(-3).

This paper reports on the results of research aimed at solving the problem of on-line monitoring of odorant in natural gas mixtures in order to make the odorization process effective and ensure the safety of main gas pipeline exploitation. Our results show that using the infrared absorption spectroscopy method is promising for this purpose. Using radiation sources operating in the spectral range 6-15 mu m allows us to obtain an odorant detection sensitivity of approximately 5 ppm in gas mixtures of different composition.

This paper reports that the use of a lock-in detection technique, when the pump current modulation of a diode laser is operating near the wavelength of 2 mu m, allows the improvement of the sensitivity of the online detection of (CO2)-C-13 in expired air by more than three orders of magnitude. The sensitivity of the (CO2)-C-13 detected in the paper is 60 ppb with an error of (CO2)-C-13 concentration measured in the exhaled breath at the level of 2.9% for an optical path length of 60 cm.

Implementing Kalman and Savitzky-Golay adaptive filters to process experimental signals and improve the sensitivity and accuracy of the measurements of the content of (CO2)-C-13 in human expiratory air with the tunable diode laser absorption spectroscopy method while using a laser diode as a tunable source in the range of 4860-4880 cm(-1) near a wavelength of 2 mu m has been reported. It is established that using these filters makes it possible to provide a detection sensitivity of (CO2)-C-13 at 5.5 . 10(14) cm(-3) with a minimum detectable fraction of (CO2)-C-13 in a mixture with( 12)CO(2) of the order 2.1 . 10(-5).

This paper reports on using the empirical mode decomposition of an experimental signal to improve the accuracy of (CO2)-C-13 detection in expired air through an absorption spectroscopy method that employs a frequency-tunable diode laser operating near a wavelength of 2 mu m. The conducted research shows that using this method can increase the sensitivity of (CO2)-C-13 detection in human exhaled breath by two orders of magnitude.