T.M. Petrova

High resolution study of the ν5 + ν12 band of C2H4

The combination band ν5 + ν12 of ethylene, C2H4, has been recorded for the first time with a high resolution Fourier transform spectrometer Bruker IFS 125HR. Assignments of transitions and preliminary rotational analysis are made. Two models (Hamiltonian of the isolated vibrational state and Hamiltonian that takes into account resonance interactions) are used. Influence of the local resonance interactions on the parameters and reproduction power of the models is discussed.

Measurements and calculations of He-broadening and -shifting parameters of the water vapor transitions of the ν 1 + ν 2 + ν 3 band

The water vapor line broadening and shift in the ν 1 + ν 2 + ν 3 band induced by helium pressure were measured using a Bruker IFS 125HR FTIR spectrometer. The measurements were performed at room temperature at a spectral resolution of 0.01 cm−1 and in a wide He pressure range. The shifting coefficients δ are mainly positive, in contrast to the line center shift induced by other mono-atomic gases. Calculations of the coefficients γ and δ were performed in the framework of the semi-classical method. The influence of the rotational dependence of the isotropic intermolecular potential and accidental resonances in the H2O molecule on the shifting coefficients is discussed. Calculated values of line profile parameters are in a good agreement with observed parameters.

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.

Line mixing in the water vapour transitions of the ν1 + ν2 + ν3 band perturbed by helium pressure

The line mixing effect for two pairs of transitions with rotational quantum numbers (3 1 2) ← (4 1 3), (3 2 1) ← (4 2 2), (4 3 1) ← (3 3 0) and (4 2 2) ← (3 2 1) in the ν1 + ν2 + ν3 band of H2O has been studied. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm−1 and in a wide pressure range of helium. Pressure-broadening and -shifting coefficients and mixing parameter were obtained with help of the line profile using the Rosenkranz first-order approximation.

Fourier Transform and Photoacoustic Absorption Spectra of Ethylene within 6035–6210 cm-1: Comparative Measurements

Measurements of ethylene absorption spectra with Fourier Transform (FT) and Photoacoustic (PA) spectrometers within 6035–6210 are described. The methodology used for building the frequency scale for both spectrometers is presented. The methane absorption spectrum, included into the HITRAN database, was used in both cases to calibrate the frequency scale. Ethylene absorption spectra were obtained with the two recording methods; a coincidence of the measured line center positions was obtained with an accuracy of 0.0005 .

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.

Fourier spectroscopy of water vapor in the volume of aerogel nanopores. Part 2. Calculation of broadening and shift of spectral lines by adsorbed molecules

The model for simulating the profile of water vapor confined in nanoporous aerogel [2] has been improved. In the improved model, we take into account a possibility of loss of rotational degrees of freedom for water molecules adsorbed on pore walls, collisions with which significantly contribute to line broadening and shifting. The half-widths and shifts calculated for this model are in a good agreement with experimental data.

Measurements and calculations of H2-broadening and shift parameters of water vapour transitions of the ν1 + ν2 + ν3 band

ABSTRACT The water vapour line broadening and shifting for 97 lines in the ν1 + ν2 + ν3 band induced by hydrogen pressure are measured with Bruker IFS 125 HR FTIR spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm−1 and in a wide pressure range of H2. The calculations of the broadening γ and shift δ coefficients were performed in the semi-classical method framework with use of an effective vibrationally depended interaction potential. Two potential parameters were optimised to improve the quality of calculations. Good agreements with measured broadening coefficients were achieved. The comparison of calculated broadening coefficients γ with the previous measurements is discussed. The analytical expressions that reproduce these coefficients for rotational, ν2, ν1, and ν3 vibrational bands are presented.