Carbon-dioxide broadened sulfur-dioxide line widths have been calculated with semi-empirical method at the room temperature (T=296K) for 621 R-branch lines of the ν1+ν3 band, rotational quantum numbers J vary in the range from 0 to 70. The computed broadening parameters are compared with the literature data, and good agreement is obtained. Semi-empirical approach is based on analytical expressions of semi-classical impact theory and including a fewparameter correction which can be determined by fitting the broadening coefficients on the experimental data.
Vibrational dependence of the line contour parameters was studied. The effects of the vibrational-rotational dynamics related to the chaotic behavior under strong excitation were considerate by analyzing the water vapor spectra. Empirical dependences on vibrational quantum numbers were analyzed.
Water vapor line broadening and shifting coefficients by nitrogen pressure were studied in the 22300-22600 cm-1 spectral range (6ν1+ν3 and 7ν1 bands) using a high resolution Fourier-transform spectrometer IFS-125M. Measurements were performed using IFS-125M Fourier transform spectrometer with a spectral resolution of 0.1 cm-1 and optical path length of 24 m. The Doppler FWHM in this region is ~0.066 cm-1. Calculations of N2-broadening coefficients were performed using a semi-empirical approach developed by using anharmonic wavefunctions determined from variational nuclear motion calculations. In this variant all scattering channels induced by collisions are taken into account.
The self-broadening coefficients and CO2-broadening coefficients of lines of the main isotope species of SO2 are estimated based on the analysis of literature data. The dependence of the self-broadening parameters on vibrational-rotational quantum numbers is evaluated. In the case of CO2 broadening, the half-widths of lines are calculated using a semiempirical method based on a parametric modification of the impact semiclassical model; the model parameters were determined from the fit to experimental data.
Self-, CO2-, N2-broadened line widths of NO2 molecule have been obtained at the room temperature for ~400 000 lines, rotational quantum numbers vary in the range: J to 70 и Ka to 20. The temperature exponents for every line were calculated. The data have been evaluated theoretically in the frame of two methods: semi-empirical approach based on analytical expressions and including a few-parameter correction to account for the real curved trajectories and averaged energy differences method. Being validated by comparison with measurements, these approaches were used to compute extensive line list which could be useful for atmospheric, astrophysical applications and spectroscopic databases.
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 averaged energy difference method was applied to calculate water vapor line broadening induced by hydrogen and helium pressure. Calculations were performed for wide ranges of rotational quantum numbers (J from 0 till 20 by the averaged energy difference method and J from 20 till 50 by interpolation of J-dependence), the spectral range is from 500 till 10 000 cm-1. The temperature exponents were calculated for every mentioned line. Comparisons of the calculated line shape parameters with the literature values are made for H2O-H2, -Не colliding systems.
Line broadening coefficients of the Н2О-Н2О system were investigated in the region 15500 – 16000 cm-1 using a high resolution Fourier-transform spectrometer IFS-125M. The White type multipass absorption cell with a basic length of 60 cm was used. Least-square-fitting algorithm WXSPE was used to retrieve of the spectroscopic parameters from measured spectral data set. Calculations of self-broadening are performed using a semi-empirical approach. This method is further developed by using anharmonic wavefunctions in the estimates of line profiles. This approach explicitly takes into account all scattering channels induced by collisions. Calculated data are in a good agreement with the measured ones.
Line broadening in the case of H2O-N2 colliding system only slightly depend on vibrational quantum indices. The largest difference in the broadening coefficients of different bands is as small as several percent. Usually the halfwidths obtained for only one band is extrapolated to other vibrational bands. Indeed, in the case of low-lying states the vibrational amplitudes are usually small in comparison to the equilibrium distances between the atoms. However, for transitions to highly excited states, the intra-molecular motion cannot be treated as small amplitude vibrations, and as a consequence, corrections due to the intra-molecular interactions are large. The vibrational dependence of the line widths was studied by a high resolution Fourier-transform spectrometer IFS-125M. Line-broadening and line-shifting coefficients derived from the fitting were compared to calculated data.
Calculations of nitrogen-broadening coefficients and their temperature exponents for methyl cyanide lines at the room temperature using semi-empirical method are presented. They were performed for wide ranges of rotational quantum numbers J and K requested for atmospheric applications: J from 0 till 70 and K from 0 till 20. The temperature exponents were calculated for every mentioned line. Extensive line lists are provided for the Earth and Titan atmosphere temperature ranges.
The quality of the spectroscopic line parameters from the HITRAN Database for remote sensing of the water vapour isotopic composition of the atmosphere is widely discussed. In this research we show that the HITRAN-2008 data for H2O isotopologues in the near infrared spectral range (4000-6400 cm-1) is reasonably good. The HITRAN data was tested with independent calculation (ab initio et al.). For the evaluation we've used two following criteria: a quality of the fitting of atmospheric spectra measured at the Ural Atmospheric Station (UAS, Kourovka) with the high-resolution Fourier-transform infrared spectrometer and an agreement between the retrieved HDO/H2O relative concentration ratios in the atmospheric column and the results of the simulation of the isotopic general circulation model ECHAM5-wiso (validated for Kourovka region).
The method to the calculation of rotation-vibrational line half-width of asymmetric top molecules is proposed. The influence of the buffer gas on the internal state of the absorbing molecule is emphasized in this method. The basic expressions of present approach are given. The averaged energy differences method was used for the calculation of H2O and HDO lines broadening. Comparisons of the calculated line shape parameters with the experimental values in different absorption bands are made.
The semi-empirical method has been used to determine of room temperature self-broadened halfwidths of methyl cyanide and CO2-broadened halfwidths of methyl chloride. We obtained data approximately for 1500 rotation-vibration transitions. J-dependences of these colliding systems are different due to various absorber-perturber resonance effects. Results of calculations clearly demonstrate a very good agreement between observed and computed parameters for both absorbing molecules.
Air-broadening coefficients of the water isotopologue HD16O up to J = 50 for P, Q and R branches calculated using
different methods are presented. For partially labeled lines (“good” quantum numbers: J, symmetry and level number)
we combined three methods for calculating half-widths: J-dependence and JJ’-dependence up to J=15 and averaging
coefficients calculated using a previously developed semi-empirical method for high J (15-50). For lines with full
assignments based on normal modes v1, v2, v3, Ka, Kc we used: (a) an analytical model (approximation) which depends
on use of rotational quantum numbers J and Ka for both the upper and lower levels; and (b) a method based on the
estimate of the averaged energy differences between coupled states. The comparison of calculated data with broadening
coefficients from HITRAN-2008 and available experimental data is presented. The resulting broadening coefficients can
be used to calculate spectra of water vapor with hundreds millions of weak lines with reasonable accuracy. The line list
VTT [Voronin, Tennyson, Tolchenov, MNRAS, 2010], supporting programs, files for calculations of spectra HD16O and
estimation of broadening coefficient are made freely available also in electronic form via http://www.exomol.com.
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