Measurements of CH3D line strengths, foreign pressure-broadening, and pressure-shift coefficients at near-IR region using continuous-wave cavity ring-down spectroscopy

Abstract

Three DFB near-IR lasers were used to measure the line strengths of CH3D ro-vibrational transitions (2ν4) in the wavenumber regions of 6017.5–6031.5cm−1 and 6046.5–6070.0cm−1 using continuous-wave cavity ring-down spectroscopy (cw-CRDS). In the wavenumber interval of 6017.5–6031.5cm−1, the strongest peak is located at 6024.697cm−1 with a line strength of 1.24×10−25cm/molecule of CH4, assuming a CH3D natural abundance of 0.0616%. In the 6046.5–6060.0cm−1 interval, the strongest peak is located at 6055.178cm−1 with a line strength of 9.31×10−26cm/molecule. In the 6060.5–6070.0cm−1 interval, the strongest peak is located at 6066.538cm−1 with line strength of 2.27×10−25cm/molecule. We measured foreign gas pressure-broadening and pressure-shift coefficients of CH3D absorption lines. The N2, O2 and CO2 pressure-broadening coefficients of CH3D are 0.064(1), 0.060(1) and 0.061(5)cm−1/atm, respectively, at the wavenumber of 6017.941cm−1 and 0.051(1), 0.052(1) and 0.046(2)cm−1/atm, respectively, at the wavenumber of 6064.286cm−1. The N2 and O2 pressure-broadening coefficients of CH3D are 0.065(2) and 0.060(1)cm−1/atm, respectively, at the wavenumber of 6066.538cm−1. The N2, O2 and CO2 pressure-shift coefficients of CH3D at the wavenumber of 6032.443cm−1 are −0.012(1), −0.012(1) and −0.013(1)cm−1/atm, respectively.