Temperature dependences for N2- and air-broadened Lorentz half-width coefficients of methane transitions around 3.38 µm

- Low temperature CH4 absorption spectrum was recorded near 3.38 μm.
- N2- and air-broadening parameters are given.
- Temperature dependence exponents have been determined.

We have measured high-resolution absorption spectra of methane broadened by N2 and air at sample temperatures between 173.0 K and room temperature. The measurements were performed based on direct laser absorption spectroscopy using a tunable diode laser combined with a temperature controlled cryogenically cooled absorption cell. These spectra have been analyzed to determine the pressure-broadened half-width coefficients as well as their temperature dependences for six singlet lines belonging to the ν3 band of methane near 3.38 μm. To our knowledge, the temperature dependence exponents for the pressure-broadened half-width coefficients are reported experimentally for the first time for six transitions of 12CH4 with intensities stronger than 4×10−20 cm−1/(molecule cm−2). The measured half-width coefficients and the temperature dependence exponents of these transitions are compared with the available values reported in the literature and the HITRAN2012 database. Agreements and discrepancies are discussed.