Absolute intensities and self-, N_2-, and air-broadened Lorentz halfwidths for selected lines in the ν_3 band of ^12CH_3D from measurements with a tunable diode laser spectrometer

Abstract

Absolute intensities were measured at room temperature for thirty-nine lines in the qQ, qP, and qR branches of the ν3 (A1) parallel-type band of 12CH3D between 1250 and 1340 cm−1 using a tunable diode laser spectrometer. Although the line intensities were determined to a precision ≈3%, the square of the vibrational transition dipole moment matrix element derived from each mean line intensity varied by ≈20%, indicating intensity perturbations possibly caused by Coriolis interaction with the nearby ν6 fundamental. Room temperature air- and N2-broadened halfwidths have also been determined for seventeen of these lines and the measured halfwidth values varied from 0.023 cm−1 atm−1 for high J,K transitions to ∼0.067 cm−1 atm−1 for low J,K transitions. The average of the ratios of N2- to air-broadened halfwidths was 1.01, with a standard deviation of 0.01, indicating almost equal broadening efficiencies for N2 and air. Room temperature self-broadened halfwidths were also determined for three transitions with a mean value of 0.0803 ± 0.0010 cm−1 atm−1.