N2 and Ar broadening and line mixing in the P and R branches of the v3 band of CH4

Iterative maximum a posteriori (IMAP)-DOAS for retrieval of strongly absorbing trace gases: Model studies for CH<sub>4</sub> and CO<sub>2</sub> retrieval from near infrared spectra of SCIAMACHY onboard ENVISAT

“…This deviation from the classical Lorentz theory is more likely for vigorously interacting molecules such as H 2 O with the known problems of continuum absorption (Clough et al, 1989;Ma and Tipping, 1999). However, Pine (1997) found deviations from the Voigt profile as well as line mixing in the ν 3 band of CH 4 at about 3300 nm (3000 cm −1 ). Since line mixing leads to a narrowing of the absorption lines, it is supposed to decrease the sensitivity of the measurement.…”

Intensities, broadening and narrowing parameters in the ν 3 band of methane

“…Benner et al [29] used a FTIR instrument at 0.01 cm -1 spectral resolution to measure N 2 -, O 2 -, air-broadening and line-shifting parameters for 450 weak methane transitions belonging to the ν3, ν 2 +ν 4 , 2ν 2 2 and 2ν 4 2 bands located in the 2650 -3200 cm -1 spectral range. These measurements were carried out at 296 K. Using a tunable diode laser spectrometer Pine [30] belonging to the ν 2 +ν4 combination band using a tunable diode laser spectrometer. In their work [31], intensities, self-, N 2 -and O 2 -broadening and shifting parameters were obtained from spectra simulation using the Voigt profile as well as the Rautian (hard-collision) and Galatry (soft-collision) models.…”

Absorption cross-section measurements of methane, ethane, ethylene and methanol at high temperatures

“…The HeNe laser measurements are carried out at a frequency of 2947.909 cm -1 which is quite close to the linecenter frequency, 2947.912 cm -1 , of the P(7) rotational transition of methane. For the P (7) transition, the collisional broadening coefficients (γ) of CH 4 -He, CH 4 -Ar and CH 4 -N 2 at 296 K are 0.048 [15], 0.056 [27] and 0.063 [27] cm -1 /atm, respectively. This dependence of methane cross-section on bath gases was also reported by Tsuboi et al [28] in their theoretical study.…”