Measurements of N2-broadening and pressure-shift coefficients in the ν3-band of 12CH4 using a cw-OPO

- We report on line shift and line broadening coefficients measurements in methane.
- We perform direct absorption spectroscopy with a cw-singly resonant OPO.
- The results agree fairly well with previous published studies.

We have measured the nitrogen-collision-induced line broadening and line shift coefficients of three singlet lines - P(1), R(0) and R(1) - belonging to the ν3 band of methane (12CH4) at 3.29-3.32 μm using direct laser absorption spectroscopy by means of a continuous-wave mid-IR optical parametric oscillator. Owing to the well-isolated features of the singlet lines, the lineshapes were modeled with a simple Voigt profile in order to retrieve the line parameter coefficients. The values of the N2-broadening and pressure-shift coefficients agree fairly well with the previously published ones that use either Fourier-transform or mid-infrared difference-frequency spectrometers along with more complex analytic spectroscopic models.