Intramolecular isotope distribution in heavy ozone (¹⁶O¹⁸O¹⁶O and ¹⁶O¹⁶O¹⁸O)

Abstract

O-containing ozone, is an essential feature of the unusual oxygen isotope effect in ozone formation. Whereas information on r 49 is sparse and of limited accuracy, precision in laboratory measurements of r 50 has recently been improved. The two most recent experiments, however, disagree on whether there is a preference for the formation of asymmetric over symmetric molecules or not (r 50 > 2 versus r 50 = 2). To throw light on this discrepancy, the temperature dependence of r 50 has been derived from a reanalysis of existing measurements: r 50 is found to decrease from 2.13 at 360 K to about 2.00 at 170 K. Kinetic model calculations show that the discrepancy between the two measurements disappears when temperature conditions for ozone formation are accounted for.

Retrievals of heavy ozone with MIPAS

“…However, it should be noted that, in the microwindows considered here, the magnitudes of the uncertainties in the spectroscopic data for 50 O 3 are not given in the HITRAN database for several key parameters, such as line position and intensity. This is likely caused by the difficulty in distinguishing between the symmetric and asymmetric isotopomers, noted by Janssen (2005). Therefore, this uncertainty is underestimated here.…”

Signature of Arctic surface ozone depletion events in the isotope anomaly (Δ<sup>17</sup>O) of atmospheric nitrate

“…It is known that the intramolecular distribution of heavy oxygen atoms in the molecule of ozone differs from a stochastically expected distribution (Janssen, 2005). The asymmetric isotopologues of ozone are enriched in heavy oxygen isotopes with respect to bulk ozone, thus the terminal atoms of the molecule carry a higher load of heavy isotopes.…”

Rapid photochemical equilibration of isotope bond ordering in O2

“…In this paper, we investigate only isotopic ordering in O 2 , which can be established independently from, and on different time scales than, the bulk isotopic partitioning that occurs between the oxygen-containing molecular species in a gas-phase photochemical system. The reader is directed to the literature on the isotope effects of O 3 formation for discussions of photochemical equilibrium between O 2 and O 3 [Janssen, 2005].…”

“…In addition, previous studies suggest that the O + O 2 recombination efficiency on Pyrex is < 1% above 100 K, with quenching of excited O 3 * on walls being orders of magnitude less likely [Macko et al, 2004;Janssen and Tuzson, 2010]. Nonetheless, both of these effects would increase the effective rate of O 3 formation, leading to enhanced photolytic generation of atomic oxygen.…”