UV Absorption Cross Sections of Acetyl Peroxynitrate and Trifluoroacetyl Peroxynitrate at 298 K

Abstract

The UV absorption cross sections of acetyl peroxynitrate (PAN) and trifluoroacetyl peroxynitrate (FPAN) were determined at 298 K in the wavelength ranges 220-325 nm and 230-305 nm, respectively. Both peroxynitrates were prepared from nitric acid and the corresponding peroxy acids in n-tridecane solution. The UV spectra were measured in a large cell (v = 420 drrr') equipped with White mirror systems for the simultaneous detection of gas phase species by long-path UV and IR absorption. Impurities in the samples were quantified by their IR and/or UV absorption, and the UV spectra were corrected for contributions from these impurities using appropriate reference spectra. Concentrations of acetyl peroxynitrate and trifluoroacetyl peroxynitrate were derived from their IR absorptions by application of Beer's law. IR absorption coefficients were determined based on pressure measurements of the pure compound (for PAN) or on the stoichiometric CO 2 yield in the thermal decomposition of the peroxynitrate in the presence of NO and 02 (for FPAN). The resulting UV absorption cross sections of PAN are larger than literature values, leading to photolysis rate constants on the Earth's surface which are higher by a factor of 4 than previous values (Senum et aI., 1984). The absorption cross sections of FPAN were measured for the first time and result in photolysis rate constants which are slightly higher than those of PAN, suggesting that CF3C(0)02N02 and, by analogy, other haloacetyl peroxynitrates have too short a lifetime in the upper troposphere to be of importance for the transport of halogens into the stratosphere. 1205

Quantum Yield of NO3 from Peroxyacetyl Nitrate Photolysis

“…For the analysis of the present data only the relative cross section at the photolysis and absorption wavelengths needs to be known. Averaging the results of Senum et al, Talukdar et al., and Libuda and Zabel we derive a value of 10.0 ± 0.4 for the ratio of PAN absorption cross sections at 214 and 248 nm, i.e where the quoted uncertainty represents 2 standard deviations.…”

Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

“…Many researchers have investigated the photolysis process of PAN (Libuda and Zabel, 1995;Talukdar et al, 1995;Flowers et al, 2007). With the further understanding of the photolysis process of PAN, the influence of photolysis processes on the loss of PAN has been gradually realized in the photochemical reaction of acetaldehyde.…”

Quantum chemical study of the atmospheric C2H5C(O)OONO2 (PPN) molecule and of the C2H5C(O)OO and C2H5C(O)O radicals

“…The formation, global distribution, and thermal chemistry of PAN have been the subject of numerous studies [6,[8][9][10][11][12][13][14][15][16][17][18]. Also its spectroscopic and photochemical properties have been well characterized [5,[19][20][21][22].…”