Extraordinary isotopic fractionation in ozone photolysis

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 17 O and 18 O isotopologue‐dependent variations as a function of altitude despite the fact that the extraordinary photolysis‐induced isotopic fractionation effect is dampened in the atmosphere due to the integration over all excitation wavelengths.