Analysis of the ν3 + ν7 combination band of CF2Cl2 from spectra obtained by high resolution diode laser and FTIR supersonic jet techniques

Abstract

High resolution (0.0011 cm⁻¹ full width half maximum) diode laser spectra have been measured for mixtures of CF₂Cl₂ in Ne, expanded in a supersonic planar jet. In addition interferometric Fourier transform infrared (FTIR) spectra have been recorded with a resolution of about 0.004 cm⁻¹ (FWHM, Hamming apodization) for neat CF₂Cl₂, expanded through a circular 200 μm nozzle. We present the analysis of the ν₃ + ν₇ combination band of CF₂³⁵Cl₂ [₀ = 888.496 89(10) cm⁻¹] and CF₂³⁵Cl³⁷Cl [₀ = 883.203 89(12) cm⁻¹]. Absolute band strengths have been measured for all bands falling in the atmospheric window (ν₃ + ν₇, ν₆, ν₁ and ν₈) and thus being important for monitoring CF₂Cl₂ in the lower troposphere and stratosphere. A Fermi resonance coupling constant W = (15 ± 2) cm⁻¹ is estimated for the resonance between ν₃ + ν₇ and ν₆ in both isotopomers.