Vibrationally excited ozone

A chemically based, mass-independent fractionation process was first observed during ozone formation through the gas-phase recombination reaction (Thiemens Heidenreich 1983) O + O2 + M - O3 + M. The product ozone possesses equally enriched heavy-oxygen isotopes I7 IS0. by approximately lOO /oo with respect to the initial oxygen, with a slope value of unity in a three-isotope oxygen plot. This discovery led to the conclusion that a symmetry-dependent reaction can produce meteoritic isotopic anomalies (Thiemens 1999, 2006). Recently, theoretical calculations of Gao Marcus (2001) established the major role of symmetry in isotopolog-specific stabilization of vibrationally excited ozone molecules that give rise to the mass-independent compositions. 

Another interesting result obtained in experiments on these ratios of rate constants is the lack of the dependence of the ratio on the nature of the gas collisionally deactivating the vibrationally excited ozone isotopomer [46]. Different mechanisms have been postulated for the collisional deactivation, including the energy transfer mechanism used here and most commonly used elsewhere, and a chaperon mechanism in which the third-body collision partner forms collision complex with the Q or with the Q2 prior to the recombination step. Recently the chaperon mechanism was revisited for ozone formation, analyzing pressure and temperature dependent data on the recombination rate [47]. Since the ratios of rate... 

Vibrationally Excited Ozone.—Ozone can be promoted to its (001) vibrational level as a result of chance coincidences between lines in the (001,000) fundamental band of Os and lines from a COa laser, the strongest overlap being with the P(30) line in the 9.6 /um band. This has been the basis for a number of experimental studies of the enhanced reactions of Osf with NO, 02( ), and SO. ... 

Adler-Golden, S.M. Franck-Condon analysis of thermal and vibrational excitation effects on the ozone Hartley continuum. J. Quant. Spectrosc. Radiat. Transf. 30, 175-185 (1983) Adler-Golden, S.M., Schweitzer, E.L., Steinfeld, J.I. Ultraviolet continuum spectroscopy of vibrationally excited ozone. J. Chem. Phys. 76, 2201-2209 (1982)... 

It is unclear exactly how the two potential surfaces, and hence the interaction regions between them, behave as the parent molecules bend. Our experimental results indicate that the more bent the ozone molecules are as they dissociate the more effectively is the available energy channelled into the OA T, ) fragment vibration. It is possible that as the parent molecules bend, the crossing seams move to a region on the repulsive state that more strongly favors the production of vibrationally excited 02(3 ) fragments. 

Ozone layer depletion, stratospheric, 21 525-529 Ozone level, reduction in, 21 528 Ozone molecules, vibrationally excited, 27 774... 

A knowledge of the kinetics of the decomposition of ozone is essential for the understanding of the chemistry of some important processes which occur in earth s atmosphere. Yet, in spite of numerous studies and the structural simplicity of ozone, the mechanism of its ultraviolet photolysis is still uncertain. Electronically and vibrationally excited species are involved in ozone decomposition and the current knowledge of the chemical behavior of such intermediates is still in its infancy. 

Finlayson, B. J., J. N. Pitts, Jr., and H. Akimoto, Production of Vibrationally Excited OH in Chemiluminescent Ozone-Olefin Reactions, Chem. Phys. Lett., 12, 495-498 (1972). 

A number of studies have measured the isotopic distribution in atmospheric ozone. There are three naturally occurring isotopes of oxygen, lftO, l70, and lxO, which might initially be expected to be represented statistically in atmospheric ozone. However, both stratospheric and tropospheric ozone have been measured to be enriched in the heavier isotopes over what one would expect statistically (e.g., see Mauersberger, 1981 Mauersberger et al., 1993 Krankowsky et al., 1995). A variety of explanations of this fractionation have been put forth, including nuclear symmetry restrictions on the 02 + O reaction that forms 03 (Hellene, 1996), the preferential dissociation of heavy ozone to form vibrationally excited 02 (u > 26) that then... 

More recent studies have made possible direct determination of the rate constants k7a and k7b. McNeal and Cook47 have followed the concentration of 02(1A9) in a discharge-flow system by the photoionization technique (Sect. III-E). In the presence of ozone, 02(1A,) decays by a predominantly first-order mechanism, so that, presumably, the second-order pooling process (11) does not contribute significantly to the loss of 02(1A9). If it is assumed that the only loss process for Oa(1A9) is reaction with ozone in reaction (7a), then k7a lies between 1 x 106 and 2 x 106 liter mole-1 sec-1. This value is considerably lower than the rate constant measured by Mathias and Schiff87 if Oa in reaction (7) is largely O Aj). McNeal and Cook consider the possibility that their photoionization current decreases by less than that expected on the basis of [02(1A9)J decay, as a result of the formation of vibrationally excited oxygen in reaction (15d)... 

Ozone was flash photolyzed in the presence of 180 enriched water and added argon (03 H20 Ar =1 1 8). Vibrationally excited OH was observed56. 

No, we have not although I should emphasize that, using the newly developed laser spectroscopic tools described in my paper, studies of the chemistry of vibrationally excited states now become feasible. Destruction of ozone following collisions with vibrationally excited molecules is known, but the importance of vibrationally excited species in the atmosphere is a matter of some debate. Collisional quenching of these molecules must always compete with chemistry and so the question becomes one of understanding the relative efficiencies of such processes. 

Mixtures of ozone (4 to 6 mm. of Hg pressure) and ammonia, hydrogen, hydrogen chloride, methane, or water (up to 150 mm. of Hg pressure) were flashed (7). In each system the spectrum of the OH radical was observed in the 0,0 1,0 1,1 2,1 2,2 and 3,2 bands of the A2S+ — system. Transitions from vibrationally excited levels were visible for 15 jujsec. and those from the zeroth level for up to 75 /jisec. In addition, the spectra of NH, O2, and CIO were recorded, the latter persisting for 1 msec. The only spectrum visible after this time was that of formaldehyde. 

When ozone is flashed with only inert gases present, vibrationally excited oxygen, O2, is produced (13) in the reaction... 

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