| Abstract
| - Absorption cross sections for the Ã1A2−X̃1A1 electronic transition of formaldehyde have been measured byultraviolet (UV) laser absorption spectroscopy in the tropospherically significant wavelength range 300−340nm, over which HCHO is photochemically active. Absorption cross sections are reported at two temperatures,294 and 245 K and at a spectral resolution of 0.0035 nm (0.35 cm-1). At this resolution, greater peak absorptioncross sections are obtained for many of the sharp spectral features than were previously reported. To simulateatmospheric conditions in the troposphere, the effects of adding a pressure of nitrogen of up to 500 Torr andof reduced sample temperature were investigated. The overall magnitudes of peak absorption cross sectionsare largely unaffected by the added pressure of nitrogen, but a modest degree of pressure broadening (0.2−0.3 cm-1 atm-1) is evident in the line shapes. Computer simulations of spectra have been optimized bycomparison with wavelength-dependent formaldehyde absorption cross sections for each major vibronic bandin the chosen wavelength range. Experimental and computer simulated spectra at 294 and 245 K are comparedto test the reliability of the computer simulations for quantification of the effects of temperature on absorptioncross sections. All experimental absorption cross section data and tables of input parameters for spectralsimulations are available as Supporting Information.
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