Diode Laser Overtone Spectroscopy of Methyl Iodide at 850 Nm

Using Tunable Diode Laser Absorption Spectroscopy (TDLAS), 82 CH3I overtone absorption lines were detected for the first time in the range between 11,660 and 11,840 cm−1 (844–857 nm), with strengths estimated around 10−27–10−26 cm/molecule. The lines were measured utilizing commercial heterostructure F–P type diode lasers, multipass cells, and wavelength modulation spectroscopy with the second harmonic detection technique. A high modulation amplitude approach was adopted for the analysis of the line shapes. Self-broadening coefficients were obtained for two lines.