The near infrared cavity-enhanced absorption spectrum of methyl cyanide

The absorption spectrum of methyl cyanide (CH ₃CN) has been measured in the near IR between 6000 and 8000cm ^-1 with a resolution of 0.12cm ^-1 using Fourier transform incoherent broadband cavity-enhanced absorption spectroscopy. The spectrum contains several weakly perturbed spectral regions; potential vibrational combination bands contributing to the spectrum are outlined. Line positions and cross-sections of CH ₃CN between 6814 and 7067cm ^-1 have been measured at high-resolution of 0.001cm ^-1 using diode laser based off-axis cavity-enhanced absorption spectroscopy. A total of 4630 new absorption lines of CH ₃CN are identified in this region. A value for the self-broadening coefficient has determined to be (3.3±0.2)×10 ^-3cm ^-1 mbar ^-1 for one isolated line at 7034.171cm ^-1. Several line series have been identified in these regions and an autocorrelation analysis performed with a view to aiding future assignments of the rotational-vibrational transitions.