The binary absorption coefficients for H2 + CO2 mixtures in the 2.12–2.35 µm spectral region determined by CRDS and by semi-empirical calculations

Highlights: • Spectra of CO₂-H₂ mixtures have been recorded at room temperature by CRDS. • Four spectral windows are covered in the 2.12–2.35 µm spectral region. • The binary coefficients $B_{C{O}_2-H_2}+B_{H_2-C{O}_2}$ have been retrieved from the spectra. • The retrieved binary coefficients are compared to semi-empirical calculations. • This comparison shows the limits of the model in the studied spectral region. Spectra of CO₂ + H₂ mixtures have been recorded at room temperature by using the cavity ring down technique, for four spectral intervals in the 2.12–2.35 µm CO₂ transparency window which is within the (1-0) band of H₂. The binary coefficients $B_{C{O}_2-H_2}+B_{H_2-C{O}_2}$ have been retrieved from the spectra recorded at different pressures after subtraction of the CO₂ monomer contribution and of the H₂-H₂ and CO₂-CO₂ collision induced absorptions (CIAs). In order to reduce the uncertainties, new measurement of the pure H₂ CIA, the main subtracted contribution, at the percent level are also reported. The new set of experimental binary coefficients is compared to values provided by semi-empirical calculations made with the assumption of an isotropic CO₂-H₂ interaction potential and neglecting the short-range interaction-induced electric dipole. This comparison shows the limits of using such a model, which is the only one available, in that spectral region.