The near infrared cavity-enhanced absorption spectrum of methyl cyanide

The absorption spectrum of methyl cyanide (CH3CN) has been measured in the near IR between 6000 and 8000 cm−1 with a resolution of 0.12 cm−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 CH3CN between 6814 and 7067 cm−1 have been measured at high-resolution of 0.001 cm−1 using diode laser based off-axis cavity-enhanced absorption spectroscopy. A total of 4630 new absorption lines of CH3CN are identified in this region. A value for the self-broadening coefficient has determined to be (3.3±0.2)×10−3 cm−1 mbar−1 for one isolated line at 7034.171 cm−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.

► Extension of the high resolution absorption spectrum of CH3CN into the near IR. ► 4630 new absorption features between 6814 and 7067 cm−1 and new unresolved bands. ► Fourier Transform cavity enhanced absorption spectroscopy (CEAS) versus off-axis CEAS.