O. V. Naumenko

An expert system for identification of lines in vibrational-rotational spectra

An expert system for automatic identification of the complex vibrational-rotational spectra of molecules has been developed. An iteration approach is implemented in this system, in which employment of the exact combination rule is combined with determination of the spectroscopic constants by solving of the inverse problems and comparison of the calculated parameters of spectral lines with the corresponding measured values. In order to calculate the energy levels and the frequencies and intensities of lines, the Watson Hamiltonian, the Padé-Borel approximants, and generating functions are used. The system is based on the application of pattern-recognition algorithms. Recognition training makes it possible to obtain the required flexibility of the system and to use different methods of identification based on the application of combination rules both for the analysis of strong bands and for the assignment of weak single lines. The system developed can be used to analyze the spectra of the Cs and C2V molecules, as well as employ the calculated spectrum of a molecule of any type prepared in advance. This system was successfully used to identify the H216O, H217O, H218O, D2O, HDO, H232S, H234S, and H233S and molecules.

Hydrogen sulfide absorption spectrum in the 5700-6600 cm -1 spectral region

High resolution FT absorption spectrum of H2S from 5700 to 6600 cm-1 was experimentally recorded and theoretically treated. As a result of the spectrum assignment 1100 precise energy levels were derived for the 2nd hexad interacting states of H232S, H233S, and H234S isotope species including the highly excited (050) state. These energy levels were modeled using Watson-type rotational Hamiltonian and taking into account Coriolis, Darling-Dennison and weak Fermi-resonance interactions inside polyad of interacting states. An average accuracy of the energy levels fitting is of 0.0019 cm-1 for the main isotope species. New evaluation of the band origin of the dark (012) state Ev = 6385.299cm-1 is obtained from the fitting process which agrees well with recent prediction by Naumenko et al. (J. Mol. Spectrosc. 50, 100-110 (2001)). Precise line intensity measurements were performed for more than 1200 absorption lines with accuracy varying from 1 to 7%. These intensities were modeled within 3.3% using wavefunctions derived in the process of the energy levels fitting. The transformed transition moment expansion with 29 terms for 1088 intensities was used. Detailed and accurate H2S absorption line list was generated in the HITRAN format for the analyzed spectral region.

Absorption spectrum of H2S between 7200 and 7890 cm-1

The high resolution absorption spectra of H2S have been recorded in the region 7200-7890 cm-1 with the McMath Fourier transform spectrometer located at Kitt Peak National Observatory. A careful analysis of the spectra led to derivation of 1080 precise energy levels for the 1st decade interacting states of H232S, H233S, and H234S isotope species. The energy levels were introduced into a least squares fit using a Hamiltonian which takes into account Coriolis, Darling-Dennison and Fermi-resonance interactions. Precise rotational and coupling parameters have been determined which reproduce the experimental energy levels with 0.0015 cm-1 for the main isotope species. The experimental band origin Ev=7419.9162 cm-1 for the super weak (220)-(000) band was obtained for the first time from the simultaneous analysis of cold (220)-(000) and hot (220)-(010) bands. Detailed and accurate H2S absorption line list was generated in the HITRAN format for the first decade spectral region.

On some new aspects in the conventional theory of vibration-rotation states of molecules

Abstract An approach which enables consideration of the problem of determining the energy spectrum of molecules containing vibrations of large amplitude within the framework of the standard Nielsen theory without the use of the Hougen-Bunker-Johns model is presented. The use of the H2O molecule as an example has shown that such an approach allows the behavior of rotational and centrifugal constants of (0v0) states with the increasing quantum number v to be described not only qualitatively but also quantitatively.

First hexad of interacting states of H2S molecule

This work is a continuation of our theoretical analyses of the H2S Fourier-transform spectrum, recorded in Kitt Peak National Observatory, in 2000 - 11,000 cm-1 spectral region. This time we deal with 4,500 - 5,600 cm-1 spectral region where the first hexad of vibrational bands (nu) 1 plus (nu) 3, 2(nu) 2 plus (nu) 3, (nu) 1 plus 2(nu) 2, 4(nu) 2, 2(nu) 1, 2(nu) 3 are placed. In comparison with the previous work significantly more precise vibrational-rotational energy levels of the analyzed vibrational states have been obtained from the spectrum assignment, which was performed with the use of special computer program. The parallel refinement of the rotational and dipole moments parameters allowed us to make reliable predictional calculations and assign not only strong lines, included in combination differences, but a weak single lines also. Finally 1052 precise vibrational- rotational energy levels for all six members of the hexad have been derived in comparison with 542 from our previous work.

The inverse spectroscopic problem for polyatomic molecules

Abstract The analysis of the possibility of deperturbation of the observed vibration-rotation energy levels and subsequent fit of each vibrational state (or only a small number of vibrational states) separately from other vibrational states are discussed.

H218O spectrum between 13000 and 15500 cm-1

The H218O spectrum has been recently investigated between 11,300 - 13,600 cm-1 covering the 3v plus (delta) spectral region where v is the quantum of the stretching vibration and (delta) is the quantum of the bending vibration. We present here the study of the 4v and 4v plus (delta) region between 13,000 and 15,500 cm-1. Spectra of 18O enriched water vapor have been recorded by means of Fourier-transform spectroscopy. The experimental details have been discussed. The experimental conditions are given.

Absorption spectra of deuterated water vapor

The HDO and D2O spectra have been recorded at room temperature with a high resolution Fourier-Transform spectrometer and a multipass cell with an absorption path length of 240 meters. The resolution used was about 0.01 cm-1, the relative uncertainty in line positions was approximately +/- 0.0002 cm-1.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fourier-transform spectrum of H2S in 2000 - 9000 cm-1

An absorption spectra of H 2 S have been recorded at 0.006 and 0.012 cm -1 resolution in 2000 - 9000 cm -1 spectral region using the Kitt Peak national observatory Fourier-Transform spectrometer. Two spectra of H 2 S at 1.49 Torr and at 9.99 Torr have been measured using non-linear least squares fitting to obtain line positions, intensities and self- broadening widths. The spectra identification has been made and twelve new bands have been assigned. The vibrational constants have been fitted to all known band centers.

V2 + v3 band of HD16O

The investigations of vibration-rotation spectra of deuterated water vapor are of great importance for the determination of intramolecular potential function, studies of molecular dynamics in excited states, and for some applications in atmospheric optics. In the present paper, the absorption spectrum of HD16O at 2 micrometers is investigated with a Fourier- transform spectrometer at a spectral resolution 0.0098 cm-1; energy levels and rotational constants of (011) vibrational state are determined.