Far-IR spectroscopy of ozone as a means of quantification of ozone isotopomers

The rotational spectrum of ozone in the far IR, obtained with a 0.004 cm(-1) resolution, has been used to quantify ozone isotopomers in an artificially produced mixture of normal and O-18 substituted ozone species. Higher order terms in the dipole operator have been found to significantly influence the theoretical line intensities of some of the rotational transitions. A planarity relation between some of the theta-constants was found in this connection. The results have been used partly to calibrate our microwave spectrometer for future ozone isotopomer quantification and partly to quantify the mixture studied. In particular the ratio r(50) between unsymmetric and symmetric species of mono-O-18 ozone has been determined with the aim of detecting possible deviations from the statistical value 2.00; for the two mixtures studied r(50) = 2.12(9) and r(50) = 2.00(8). (C) 1996 Academic Press, Inc.