A. M. Solodov

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.

Influence of the shift H2O absorption lines with air pressure on the accuracy of the atmospheric humidity profiles measured by the differential-absorption method

The variation with pressure of the centers of absorption lines of atmospheric H(2)O has been investigated experimentally using ruby and neodymium lasers. A numerical analysis of possible errors resulting from pressure shifts in the solutions of the inverse problem in remote laser sensing of vertical humidity profiles has been made.

Helium-induced halfwidths and line shifts of water vapor transitions of the ν 1 + ν 2 and ν 2 + ν 3 bands

The collisional broadening (γ) and shift (δ) coefficients of more than 100 absorption rovibrational lines of the ν 1 + ν 2 and ν 2 + ν 3 bands of the water vapor molecule in a H2O–He mixture were measured with the help of a Fourier-transform spectrometer over a large range of helium pressures. The shift coefficients δ are mainly positive and have an unusual rotational dependence, in contrast to the line center shift induced by other mono-atomic gases. The calculations of coefficients γ and δ are performed in the framework of the semi-classical method. The rotational dependence of these shift coefficients is explained by the rotational dependence of the isotropic intermolecular potential. The influence of accidental resonances in the H2O molecule is also discussed.

Broadening and shift of lines of the ν2 + ν3 band of water vapor induced by helium pressure

The broadening and shift coefficients of more than 100 absorption lines of the ν2 + ν3 band of water vapor that are induced by the pressure of helium are measured and calculated. The broadening and shift coefficients are obtained from analysis of the room-temperature absorption spectra of an H2O-He mixture measured with a resolution of 0.007 cm−1 on a Fourier spectrometer in a large range of helium pressures. The specific features in the rotational dependence of the line center shifts are determined, which, in contrast to the broadening induced by other gases, are mainly positive. The calculated coefficients of the line broadening and shift of line centers are determined by a semiclassical method. An unusual dependence of the shift coefficients is explained by the rotational dependence of the intermolecular isotropic interaction potential.

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.

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.

A Fourier-spectrometer with a 30-m base-length multipass cell for the study of weak absorption spectra of atmospheric gases

The design and specifications of the experimental set-up, consisting of an IFS-125 HR Fourier spectrometer and a 30-m base length multipass cell with the White optical system, are described. An optical path length of more than 600 m is attained. Results of measurement of atmospheric air spectra with a spectral resolution of 2 × 10−2 cm−1 and a sensitivity of less than 10−8 cm−1 are presented. It is shown that the complex reliably detects very weak absorption spectra of atmospheric molecules, including their isotopic modifications.

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.

Shift of the centers of H2O absorption lines in the region of 1.06 μm

The shift coefficients for the lines of the ν1 + ν2 + ν3 and ν2 + 2ν3 bands of H2O in the region from 9403 to 9413 cm−1 are measured and calculated. The measurements are performed using an intracavity laser spectrometer based on a neodymium laser with a determination error of the line center of 0.003–0.004 cm−1. The Ar, Kr, and Xe noble gases, as well as nitrogen, oxygen, and hydrogen were used as buffer gases. The coefficients of shifts in eight H2O absorption lines induced by oxygen, nitrogen, and atmospheric air pressures fall into the region from −0.004 to −0.069 cm−1/bar. The calculations are performed by a semiempirical method using variational wave functions, which, in contrast to other studies, correctly takes into account intramolecular interactions. The calculated values agree satisfactorily with experimental data.