Mid- and long-wave infrared absorption cross sections for acetonitrile

Infrared absorption cross sections for acetonitrile (methyl cyanide; CH3CN) have been determined in the 880-1700 cm−1 spectral region from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125 HR) and a multipass cell with a maximum optical pathlength of 19.3 m. Spectra of acetonitrile/dry synthetic air mixtures were recorded at 0.015 cm−1 resolution (calculated as the Bruker instrument resolution of 0.9/MOPD) at a number of temperatures between 203 and 297 K and pressures appropriate for atmospheric conditions. Intensities were calibrated using three composite acetonitrile spectra recorded at the Pacific Northwest National Laboratory. These absorption cross sections will provide an accurate basis for upper tropospheric/lower stratospheric retrievals of acetonitrile in the mid-infrared spectral region from ACE satellite data.

► Acetonitrile infrared absorption cross sections have been determined from 880 to 1700 cm−1. ► These cover temperatures from 203 to 297 K and appropriate atmospheric pressures. ► These cross sections will allow retrievals of acetonitrile profiles from ACE satellite data.