Determination of the vinyl fluoride line intensities by TDL spectroscopy: the object oriented approach of Visual Line Shape Fitting Program to line profile analysis

Abstract

In this work the self-broadening coefficients and the integrated line intensities for a number of ro-vibrational transitions of vinyl fluoride have been determined for the first time by means of TDL spectroscopy. The spectra recorded in the atmospheric window around 8.7 µm appear very crowded with a density of about 90 lines per cm⁻¹. In order to fit these spectral features a new fitting software has been implemented. The program, which is designed for laser spectroscopy, can fit many lines simultaneously on the basis of different theoretical profiles (Doppler, Lorentz, Voigt, Galatry and Nelkin–Ghatak). Details of the object oriented implementation of the application are given. The reliability of the program is demonstrated by determining the line parameters of some ro-vibrational lines of sulphur dioxide in the ν₁ band region around 9 µm. Then the software is used for the line profile analysis of vinyl fluoride. The experimental line shapes show deviations from the Voigt profile, which can be well modelled by using a Dicke narrowed line shape function. This leads to the determination of the self-narrowing coefficient within the framework of the strong collision model.

Keywords:

• vinyl fluoride
• line parameter determination
• line shape fitting software
• weak and strong collision models
• Voigt and Dicke narrowed profiles

Acknowledgements

The authors thank Professor P.L. Varghese for the code for the computation of the Galatry function. The authors also gratefully thank Professor J. M. Flaud for the SO₂ data about ν₁ and ν₁ + ν₂ − ν₂ upon which the assignments have been made. This work was financially supported by PRIN 2007 (project: “Trasferimenti di energia, carica e molecole in sistemi complessi”).