Extraordinary isotopic fractionation in ozone photolysis

Abstract

Analysis of experimental ozone absorption spectra reveals that ultraviolet photolysis within the structured Huggins band yields extraordinary wavelength-dependent isotopic fractionation, oscillating between complete enrichment and complete depletion for changes of less than 2 nm in the excitation wavelength. Visible photolysis yields wavelength-dependent fractionation that varies from -300‰ to +300‰. Photochemical modeling demonstrates photolysis contributes fractionation up to +45‰ to the heavy ozone anomaly in the middle stratosphere with measurable 17O and 18O isotopologue-dependent variations as a function of altitude despite the fact that the extraordinary photolysisinduced isotopic fractionation effect is dampened in the atmosphere due to the integration over all excitation wavelengths. Copyright 2005 by the American Geophysical Union.