A. A. Solodov

Water vapor continuum absorption in near-IR atmospheric windows

The near-infrared water vapor absorption is measured in the 2000–8000 cm−1 spectral region. Spectra were recorded using an IFS 125 HR Fourier spectrometer at a temperature of 287 K and a spectral resolution of 0.03 cm−1. The water vapor continuum absorption spectrum is retrieved using the known absorption in the 2500 cm−1 region as a reference point. It is shown that the continuum absorptions in four windows differ by no more than 20% under investigation conditions. This contradicts the MT_CKD continuum model, which predicts a much stronger variability of the continuum in these windows.

Spectroscopic nanoporometry of aerogel

The sizes of aerogel nanopores from the measured broadening of rotational-vibrational CO lines caused by collisions with nanopore walls have been determined. It has been shown that the sizes of nanopores with a diameter of 15–25 nm can be reliably assessed from the half-widths of spectral lines measured on a high-resolution Fourier spectrometer and agree well with the experimental data found from the low-temperature adsorption of nitrogen.

Observation of a forbidden vibrational absorption band of H2 in nanoporous aerogel

Room-temperature absorption spectra of H2 in nanoporous aerogel with a pore diameter of ∼20 nm have been studied on a Fourier spectrometer in the spectral range of 4000–4800 cm−1. Absorption at the forbidden transitions of the 0–1 vibrational band has been observed. The recorded spectra of H2 in aerogel have been compared with the spectra of free high-pressure H2.

CO2 absorption in band wings in near IR

The CO2 absorption was measured in the 7000 and 8000 cm–1 regions. The absorption coefficients were calculated using the asymptotic line wing shape theory. Line shape parameters were found from fitting to experimental data. The calculation results agree well with the measurement data. According to the line wing theory, the absorption in the band wings is caused by the wings of strong lines of an adjacent band. Within these assumptions, experimental and calculated data on the CO2 absorption coefficient in the band wings in the 7000 and 8000 cm–1 regions can provide information on the line shape at frequency detuning from several tens to several hundreds of half-widths. The results support the hypothesis that line shape parameters in the line wings related to transitions with the same initial state are close to each other. Deviations from a Lorentzian profile are found for some CO2 bands and turn out different for the wings of different bands

Measurements and calculations of Ar-broadening parameters of water vapour transitions in a wide spectral region

ABSTRACT The water vapour line-broadening (γ) and shift (δ) coefficients for 310 lines of 10 vibrational bands ν1, ν3, 2ν2, ν1+ ν2, ν2+ ν3, 2ν2 +ν3, 2ν1, ν1+ ν3, 2ν3 and ν1 +2ν2 induced by argon pressure were measured with a Bruker IFS HR 125 spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm–1 and over a wide pressure range of Ar. The calculations of the broadening coefficients γ and δ were performed in the framework of the semi-classical method. The intermolecular potential was taken as the sum of the atom–atom potential and the vibrationally and rotationally dependent isotropic induction+dispersion potential. The measured γ and δ were combined with literature data for the ν2 and 3ν1+ν3, 2ν1+2ν2+ν3 vibrational bands, and the optimal sets of potential parameters that gave the best agreement with the measured broadening coefficients for each vibrational band separately were found. Then, combined experimental data of 13 vibrational bands of H2O perturbed by Ar were used to determine the analytical dependence of some potential parameters on vibrational quantum numbers.

Spectrometric complex for investigation of spectra of selective and nonselective gas absorption in a wide spectral range

A spectrometric complex for investigation of absorption spectra in a wide spectral range (from 500 to 40000 cm–1) with high threshold sensitivity to the absorption coefficient is presented. The complex was designed at the Institute of Atmospheric Optics, SB RAS. The description of the cell and optical scheme is given, as well as specifications of the complex as compared to other world analogues. Results of the complex use for study spectra of selective and nonselective absorption of molecular gases and recording absorption spectra of molecules confined in optically transparent nanoporous structures are considered.

Fourier spectroscopy of water vapor in the volume of aerogel nanopores. Part 1. Measurements and calculations

Broadening and shifting of absorption lines of water vapor confined inside aerogel nanopores have been studied with the help of a IFS 125 HR Fourier spectrometer in the region 5000–5600 cm−1. It is shown that strong spatial limitation of molecular movement results in significant broadening and shifting of spectral lines. A semiempirical model for description of the form of absorption line contours for H2O molecules confined inside aerogel nanopores, taking account of the dependence of spectral line half-width on rotational quantum numbers, is presented for the first time. Values of spectral line half-widths found experimentally and theoretically are in good agreement.

Parameters of broadening of water molecule absorption lines by argon derived using different line profile models

The water vapor absorption spectrum was measured in the spectral region 6700–7650 cm–1 with argon as a buffer gas. The room-temperature spectrum was measured using a Bruker IFS 125-HR Fourier Transform Spectrometer with high signal-to-noise ratio, with a spectral resolution of 0.01 cm–1, at argon pressures from 0 to 0.9 atm. The H2O absorption spectral line parameters are derived by fitting two line shape profiles (Voigt and speed-dependent Voigt) to the experimental spectrum. It is shown that the use of speed-dependent Voigt profile provides the best agreement with experimental data.

Infrared absorption spectra of CO2, C2H4, C2H6 in nanopores of SiO2/Al2O3 aerogel

Transformation of C2H4, CO2 and C2H6 absorption spectra confined in nanopores of SiO2/Al2O3 aerogel is studied for the first time in comparison with the spectra of these molecules in the free state. It is shown that the integral intensities of confined C2H4 within 5700–6250 cm–1, CO2 within 4760–5160 cm–1, and C2H6 within 2830–3030 cm–1 are higher by 13.3, 15, and 18 times, respectively, than those of free gases.

Water vapor continuum absorption in the 2.7 and 6.25 μm bands at decreased temperatures

High-resolution Fourier transform spectroscopy laboratory measurements of pure water vapor absorption have been performed for the first time at temperatures from–9 to 15°С in the near-IR spectral region. As the result, the water vapor continuum absorption is retrieved within 1600 and 3600 cm–1 absorption bands (6.25 and 2.7 μm, respectively). Spectral features of the continuum retrieved at 15°С are in good agreement with the known data. It is shown that different spectral peaks of the continuum have different temperature dependencies.