The effect of pressure and excitation energy on the isotopic fractionation in the formation of ozone by discharge of O2

Abstract

Studies were made to determine the effect of the variation of the isotopic composition of initial O2, discharge energy increase and the pressure on the isotopic composition of the O3 produced from molecular oxygen. An RF generator with several frequency modes, the highest one at 3 MHz was used for the excitation of O2 molecules. The pressure of the initial O2 gas was varied from 2 to 15 cm Hg. The isotopomeric patterns produced by this generator are moderately different from those by an RF generator of lower frequencies. We used oxygen gases of three different isotopic compositions. The slope of δ233/δ234 varied with composition and pressure continuously between 1.19 to -1 2, passing values of ±∞. The significance of this is that 17O and 18O enrichments in this reaction can take place independent of one another. All data are compatible with a model based on the anharmonic predissociation of vibrationally hot O3. The theory has two parameters p and q which depend on the distribution of vibrational states of ozone as affected by the symmetry. Several investigations are suggested by our results, including the possible explanation for the oxygen isotope anomalies found in meteorites. © 1987.