Mass spectrometric analysis of nonequilibrium oxygen isotopic mixtures undergoing UV photolysis has been employed to study three-body recombination rate coefficients for the O+O2, Q+O2, O+Q2, and Q+Q2 (O=16O, Q=18O) reactions, all with M=80% N2:10% O2:10% Q2 at 200 Torr and 296 K. kO+O2 is in good agreement with the currently recommended value, while kQ+Q2 is only slightly smaller. Surprisingly, kQ+O2 is close to kO+O2, while kO+Q2 is ≈50% larger. As a consequence of this unusual behavior, kO+OQ must be ≈20% larger than kQ+OQ to produce the well-known enrichments that occur in the free atmosphere and in laboratory experiments involving scrambled mixtures. Contrary to what is usually assumed in discussions of the heavy ozone anomaly, these results indicate that isotopic asymmetry does not guarantee a rate coefficient advantage.

Laboratory experiments have been performed with O and O2 in their ground electronic states to study the distribution of all possible ozone isotopes formed. Results show that with respect to 48O3 the two symmetric molecules 17O17O17O and 18O18O18O are depleted, in good agreement with standard recombination theory. A large enrichment of about 18% is found in the asymmetric molecule 16O17O18O, while all others carry about 2/3 of that. A comparison with past laboratory and stratospheric ozone isotope measurements leads to the following conclusion: There is a standard enrichment which resides in asymmetric molecules only. It will lead to an enrichment of stratospheric 49O3 and 50O3 of 8 to 9%; this has been actually observed in recent balloon experiments. Occasionally, the enrichments in the stratosphere are larger, reaching 40% at certain altitudes. Only when ozone was formed in an electric discharge process have larger enrichments been measured in laboratory experiments, affecting both symmetric and asymmetric molecules. The results provide an important connection between numerous laboratory studies and stratospheric measurements.

Exchanges of methane and carbon dioxide between the atmosphere and the Arctic tundra were measured continuously near Bethel, Alaska (61ø05.41'N, 162ø00.92'W), for 5 weeks during July and August 1988. Fluxes were obtained directly using eddy correlation at 12-m altitude, and concentrations were measured sequentially at eight altitudes between 0 and 12 m. A prototype differential infrared absorption methane instrument based on a Zeeman-split HeNe laser was used for determination of methane and a flame ionization detector for total hydrocarbons (TI-IC). Methane was found to account for nearly all the THC concentrations and fluxes. Methane fluxes at the tower site were apportioned to various methane-producing habitats, using a satellite image to classify surface vegetation at 20 x 20 m resolution. The "footprint" of the tower was computed using a Gaussian plume model for dispersion in the surface layer. . About 6% of the seasonal net uptake was returned to the atmosphere as methane.

A spectrometer capable of detecting ozone absorption features 9 orders of magnitude weaker than the Hartley band has been employed to investigate the molecule's near‐infrared absorption spectrum. At this sensitivity a wealth of information on the low‐lying electronically excited states often believed to play a role in atmospheric chemistry is available in the form of vibrational and rotational structure. We have analyzed these spectra using a combination of digital filtering and isotope substitution and find evidence for three electronically excited states below 1.5 eV. The lowest of these states is metastable, bound by ∼0.1 eV and probably the 3A2 rather than the 3B2 state. Its adiabatic electronic energy is 1.24±0.01 eV, slightly above the dissociation energy of the ground state. Two higher states, at 1.29±0.03 and 1.48±0.03 eV, are identified as the 3B2 and the 3B1, respectively. Combined with other recent theoretical and experimental data on the low‐lying electronic states of zone, these results imply that these are, in fact, the lowest three excited states; that is, there are no electronically excited states of ozone lying below the energy of O(3P) + O2(3∑−, υ = 0). Some of the implications for atmospheric chemistry are considered.

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