UV absorption cross sections of HO2NO2 between 343 and 273 K

The UV absorption spectrum of gas phase HO2NO2 (PNA, peroxynitric acid) was measured over the wavelength range 220 to 350 nm at temperatures between 273 and 343 K using a diode array spectrometer. Contributions to the measured spectra from HNO3, H2O2 and NO2 were subtracted by using mass spectral detection of HNO3 and H2O2 and UV/Vis absorption for NO2. Our HO2NO2 absorption spectra have been scaled to the previously reported absorption cross section data of Molina and Molina [L. T. Molina and M. J. Molina, J. Photochem., 1981, 15, 97] and Singer et al. [R. J. Singer, J. N. Crowley, J. P. Burrows, W. Schneider and G. K. Moortgat, J. Photochem. Photobiol., A: Chemistry, 1989, 48, 17] at 250 nm. Our measured HO2NO2 cross sections at wavelengths longer than 290 nm are compared with literature values and the discrepancies are discussed. An empirical parametrization of the measured HO2NO2 cross section temperature dependence for use in atmospheric model calculations is presented.