Low temperature mid-infrared cross-sections for peroxyacetyl nitrate (PAN) vapour G. Allen1, J. J. Remedios1, and K. M. Smith2 1EOS, Space Research Centre, Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK 2Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot, Oxon, OX11 0QX, UK
Abstract. Laboratory absorption spectra of peroxyacetyl nitrate (PAN, CH3C(O)OONO2) vapour have been measured
in the mid-infrared range 550 cm-1 to 1400 cm-1 (18.2 to 7.14 µm) at both 250 K and 273 K, using a Fourier transform
infrared spectrometer at a nominal spectral resolution of 0.25 cm-1 (unapodised).
In addition, the 1600 cm-1 to 2200 cm-1 (6.25 to 4.54 µm) spectral
region has been measured at 250 K. Cross-sectional data at each temperature, as well as
integrated band intensities and peak infrared absorptivities for nine absorption bands of PAN in this spectral range, have
been derived from a
total of twelve separately measured PAN transmission spectra. A general increase in the peak absorption cross-section for all bands
is noted with decreasing temperature, with cross-sectional increases
in the range 6% (for the 1842 cm-1 band) and 30% (for the
991 cm-1 band) at 250K, relative to those previously reported at
295K. Differences in integrated band intensities range from -22% to
+16% for the 1741 cm-1 and 991 cm-1 bands respectively over
the same temperature range. These new absorption cross-sections for PAN are
the first to be reported at temperatures below 295 K, allowing the
of improved retrievals of the atmospherically important PAN species
from remotely sensed infrared spectra of the cold upper troposphere. These new cross-sectional data accompany this paper as an electronic supplement.
Citation: Allen, G., Remedios, J. J., and Smith, K. M.: Low temperature mid-infrared cross-sections for peroxyacetyl nitrate (PAN) vapour, Atmos. Chem. Phys., 5, 3153-3158, doi:10.5194/acp-5-3153-2005, 2005.