Methane (CH4) is a greenhouse gas which directly influences climate changes on the planet. One of the sources of methane emissions in the atmosphere during human agricultural activities is the decay of animal manure and organic components of agricultural effluents. Therefore, remote control and measurement of the concentrations of agricultural products (mainly methane), which are essentially an anthropogenic factor of the impact on the atmosphere, is important. Here, we consider a possibility of creating a mobile laser absorption complex for methane monitoring at cites with agricultural effluents.
In this work, photodetectors with a built-in cooling system based on Peltier elements and with a cooling system based on a Dewar flask filled with liquid nitrogen are experimentally studied with the aim of practical estimation and comparison of capabilities of the photodetectors with different photosensitive element cooling types.
The 13CH4 absorption spectra in the range between 7400 and 7600 cm-1 have been recorded at 4 temperatures from 296 K to 200 K using a Fourier transform spectrometer at pressures from 91 to 300 hPa, and at a 0.03 cm-1 spectral resolution. A 220 long cm cell was used, which provided a threshold sensitivity to absorption of the order of 10-6 cm-1. Empirical values of the lower state energy levels were derived from the intensity ratios of the lines measured at 200 K, 254 K, 296 K and 305 K. Line assignment of the ν2 +2ν3 band of the 13CH4 molecule was performed.
The main objective of this study is the ability to determine pore sizes in the studied finely dispersed materials by the characteristics of the interaction of water with a nano-volume. The spectra of water in nanoporous materials S.A. C30M, ssp2t8 were recorded. The spectral features of nanoporous materials were analyzed by varying the amount of water in the pores. The spectral features are compared with previously obtained data for calibrated SiO2 pores of various diameters.
The methane absorption spectra in the range between 6600 and 9200 cm-1 have been recorded at 296 K and 109 K by the Fourier spectrometer IFS – 125M at pressures from 11 to 300 mbar, and spectral resolution 0.03 cm-1. Low temperature cell with a length of 220 cm was used, which provided the threshold sensitivity to absorption of the order of 10-7 cm-1. Empirical values of the lower state energy level were derived from the intensity ratios of the lines measured at 200 K and 296 K. Line assignment of the the 3ν3 band of the 12CH4 molecule was performed. The parameters of Voigt, SDV, HTP contours (the line center, intensity) were determined at 296K.
The 12CH4 absorption spectra in the range between 6600 and 12000 cm-1 have been recorded at 296 K and 200 K by the Fourier spectrometer IFS – 125M at pressures from 11 to 300 mbar, and spectral resolution 0.03 cm-1. Low temperature cell with a length of 220 cm was used, which provided the threshold sensitivity to absorption of the order of 10-7 cm-1. Empirical values of the lower state energy level were derived from the intensity ratios of the lines measured at 200 K and 296 K. Line assignment of the the 3ν3 band of the 12CH4 molecule was performed. The parameters of Voigt contour (the line center, intensity) were determined using multi-fitting procedure at 296K.
The results of preliminary studies narrowband scattering of laser radiation with a wavelength of 532 nm of the complex system of "airgel - water", depending on the water content in airgel nanopores are presented. In order to study the scattering in nanoporous media broadband radiation two versions of photoacoustic calorimeter are tested.
The dynamic of the D2О in silica airgel absorption spectra in 4000…6000 cm-1 were recorded using Fourier Transform spectrometer FS-125M at room temperature and pressure of 23.4 mbar with spectral resolution of 0.03 cm-1. It is shown that the D2O dimers to make a significant contribution into absorption when nanopores filled with gas molecules is small. Is present a detailed description of techniques for processing the primary experimental data.
The absorption spectra of the D2О monomer in 3600…4200 cm-1 were recorded using Fourier Transform spectrometer FS-125M at room temperature and pressure of 15 and 33 mbar with spectral resolution of 0.03 cm-1 using 2.5 cm long absorption cell. Strong unblended D2O lines lying on the wing of the H2O stretching band were used to determine the line broadening parameters. They were determined from the line profile by Program VxpProfile. The differences between fitted line profiles and experimental ones do not exceed 2%. Registered D2O lines belong to (011) - (000) and (110) - (000) bands of the second triad. Self-broadening coefficients vary from 0.27 cm-1/atm to 0.445 cm-1/atm and they exceed 3 times the D2O-N2 line broadening coefficients in the v3. Calculations of self-broadening coefficients of the D2O lines were performed using semiempirical method based on the impact theory of broadening and included the correction factors. The calculated results well agree with experimental data.
The D2O absorption spectra adsorbed on the nanoporous airgel SiO2 walls in the spectral range 4200 ... 5400 cm-1 are recorded. Two types of sample with pores of 60 nm wide - the nitrogen gas-treated and untreated airgels were examined. The untreated sample was prolonged evacuation and filling by the D2O saturated vapor. The nitrogen gas-treated sample was short-time pumping, accompanied by treatment with dry nitrogen, and re- lapping by the saturated vapor. As a result, the recorded absorption spectra were shown the changes the hydrophilic properties of the nanopores walls by modernity surface in the presence of nitrogen.
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