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Abstract

A tunable diode laser absorption spectrometer operating in the 10 μm range is described, which for the first time permits simultaneous detection and quantification of the five naturally most abundant ozone isotopomers: ¹⁶O₃,¹⁶O¹⁶O¹⁸O, ¹⁶O¹⁸O¹⁶O, ¹⁶O¹⁶O¹⁷O, and ¹⁶O¹⁷O¹⁶O. Ozone samples of 25 μmole size are analysed with an estimated accuracy of 6‰ (2σ). This level of accuracy is demonstrated by comparing spectroscopically determined isotopologue enrichments of ¹⁶O₂ ¹⁷O and ¹⁶O₂¹⁸O with mass spectrometer measurements. Samples for the comparison were generated from natural oxygen in an electric discharge under two different pressure conditions. The precision obtained is sufficient to study both the isotopic and the symmetry dependence of the unique oxygen isotope anomaly in ozone formation, which shows isotopomer specific fractionation values well in the 10% range.