Spectral line parameters including temperature dependences of air-broadening for the 2←0 bands of 13C16O and 12C18O at 2.3μm

The first air broadening line shape parameters were determined for the 2 ← 0 bands of 13C16O near 4166.8 cm−1 and 12C18O near 4159.0 cm−1. Air-broadened Lorentz half-width coefficients, their temperature dependence exponents; air-induced pressure shift coefficients, their temperature dependences; and air line mixing coefficients were measured. Additionally, speed-dependent line shapes with line mixing employing the off-diagonal relaxation matrix element coefficients were applied to minimize the fit residuals. Finally, individual line positions and line intensities of the two isotopologues were constrained to the well-known theoretical quantum mechanical expressions in order to obtain the rovibrational (G, B, D and H) and band intensity parameters (including Herman–Wallis coefficients). For this, laboratory spectra were recorded at 0.005 cm−1 resolution using a temperature-controlled coolable absorption cell configured inside a Bruker IFS 125HR Fourier transform spectrometer. Gas temperatures and pressures for the spectra varied from 150 to 298 K and 20 to 700 Torr, respectively. Results were obtained from broad-band multispectrum least-squares fitting of the 4000–4360 cm−1 spectral region. Four isotope-enriched pure sample spectra and twelve spectra with air + CO samples (13C16O or 12C18O, as appropriate) were fitted simultaneously. The results obtained for 13C16O and 12C18O are compared and discussed.