High resolution mid-infrared cross-sections for peroxyacetyl nitrate (PAN) vapour

Absorption spectra of peroxyacetyl nitrate (PAN, CH3C(O)OONO2) vapour at room temperature (295 K) have been measured in the mid-infrared range, 550?2200 cm?1 (18.2?3.33 µm), using a Fourier transform infrared spectrometer at instrument resolutions of 0.25 and 0.03 cm?1 (unapodised). Both cross-section data and integrated absorption intensities for the five principal bands in the PAN spectra in this spectral range have been derived from fourteen separate PAN transmission spectra measurements. Band intensities and band centre absorptivities are also reported for four weaker PAN absorption bands in the mid infrared for the first time. These observations are the highest spectral resolution measurements of PAN bands recorded in the infrared to date. For three of the five strongest bands, the absolute integrated absorption intensities are in excellent agreement with previous studies. A 4.8% lower integrated intensity was found for the 1741 cm?1 ?as (NO2) PAN absorption band, possibly as a result of the removal in this work of spectra affected by subtle acetone contamination, while a 10.6% higher intensity was determined for the 1163 cm?1 ? (C-O) absorption band. No direct effects of spectral resolution were observed. The improved accuracy of these absorption cross-sections will allow more accurate investigations of PAN using infrared spectroscopy, particularly for remote sensing of PAN in the atmosphere.