Lineshape models testing on CH4 spectral line 6105.6257 cm−1 (R9F1, R9F2) of 2ν3 band broadened by N2 and Ne

- Methane spectra measured using two-channel photo-acoustic spectrometer with 1.65 μm diode laser.
- Lineshape models, including Dicke narrowing and speed dependent effects were tested on CH4 line.
- Even the complicated line profile models remain the systematic residuals of about 1%.
- Considered line profiles give line intensities 2% over Voigt model.
- One-by-one fitting exhibits nonlinear pressure dependence of the narrowing parameters.

The experimental spectra of CH4 absorption lines in the spectral region of 6105-6107 cm−1 have been measured in binary mixtures with N2 and Ne by a high-resolution photo-acoustic laser spectrometer. Lineshape models, including Dicke narrowing and speed dependent effects were used to CH4 spectral line (ν0 = 6105.62 573 cm−1) fitting. The hard-, soft-collision and speed dependence models lead to better fits of experiments than the Voigt profile, but the systematic residuals and biases in the retrieved line parameters are remained.

Experimental residuals of the methane spectra broadened by: N2 (a) and Ne (b) for a different line profiles.