Semi-empirical calculation of 12CH3D-H2 broadening coefficients and their temperature-dependence exponents for rovibrational lines in parallel bands

Abstract

Hydrogen-broadening coefficients and their temperature-dependence exponents for 12CH3D (J, K) lines in the parallel (ΔK = 0) ν3 band are computed by a semi-empirical method employing analytical Anderson-type expressions with a few-parameter correction factor introduced to account for various deviations from Anderson's theory approximations. On the basis of experimentally observed J-dependences of line widths, this correction factor is taken in the traditional two-parameter form, and the parameters are determined from fits on some room-temperature measurements. After validation by comparison with available experimental data, the calculations are done for extended ranges of rotational quantum numbers (0 ≤ J ≤ 70, 0 ≤ K ≤ 20) typically requested for spectroscopic databases. To get the temperature-dependence exponents, computations with the room-temperature parameters’ values are repeated for various temperatures in the room-temperature containing range 200–400 K recommended for HITRAN and least-squares fit procedures are applied. Detailed P-Q-R-line lists are provided. With negligible vibrational dependence of CH3D line widths, these data can be also employed for other A1-type bands.