Highly vibrationally excited O(2)(X(3)sigmag(-), v >/= 26) has been observed from the photodissociation of ozone (O(3)), and the quantum yield for this reaction has been determined for excitation at 226 nanometers. This observation may help to address the "ozone deficit" problem, or why the previously predicted stratospheric O(3) concentration is less than that observed. Recent kinetic studies have suggested that O(2)(X(3)sigmag(-), v >/= 26) can react rapidly with O(2) to form O(3) + O and have led to speculation that, if produced in the photodissociation of O(3), this species might be involved in resolving the discrepancy. The sequence O(3) + hv --> O(2)(X(3)sigmag(-), v >/= 26) + O; O(2)(X(3)sigmag(-), v >/= 26) + O(2) --> O(3) + O (where hv is a photon) would be an autocatalytic mechanism for production of odd oxygen. A two-dimensional atmospheric model has been used to evaluate the importance of this new mechanism. The new mechanism can completely account for the tropical O(3) deficit at an altitude of 43 kilometers, but it does not completely account for the deficit at higher altitudes. The mechanism also provides for isotopic fractionation and may contribute to an explanation for the anomalously high concentration of heavy O(3) in the stratosphere.

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Vibrational overtone excitation is, in general, inefficiently stimulated by photons, but can under some circumstances be efficiently stimulated by electrons. Here, we demonstrate electron mediated vibrational overtone excitation in molecular collisions with a metal surface. Specifically, we report absolute vibrational excitation probabilities to n ¼ 1 and 2 for collisions of NO(n ¼ 0) with a Au(111) surface as a function of surface temperature from 300 to 985 K. In all cases, the observed populations of vibrationally excited NO are near those expected for complete thermalization with the surface, despite the fact that the scattering occurs through a direct ''single bounce'' mechanism of sub-ps duration. We present a state-to-state kinetic model, which accurately describes the case of near complete thermalization (a regime we call the strong coupling case) and use this model to extract state-to-state rate constants. This analysis unambiguously shows that direct vibrational overtone excitation dominates the production of n ¼ 2 and that, within the context of our model, the intrinsic strength of the overtone transition is of the same order as the single quantum transition, suggesting a possible way to circumvent optical selection rules in vibrational pumping of molecules. This result also suggests that previous measurements of vibrational relaxation of highly vibrationally excited NO exhibiting highly efficient multi-quantum jumps (Dn $ À8) are mechanistically similar to vibrational excitation of NO(n ¼ 0).

Experimental evidence is given that supports the possibility of a previously unknown non‐LTE mechanism for stratospheric ozone formation, which could have a significant impact on the stratospheric ozone budget even if the quantum yield for production of highly vibrationally excited O2 in reaction (1), (averaged over all wavelengths shorter than 243nm) were as low as 0.2%. Stimulated emission pumping enabled preparation of individual vibrational states of O2(X³Σg−,19≤v≤27) and laser induced fluorescence was used to follow the time evolution of the prepared states and thereby determine the vibrational‐state‐specific total‐removal rate‐constants for relaxation by O2 and N2 at 295K. Self‐relaxation shows a sharp threshold for enhanced relaxation near the energy of O2(X³Σg−, v=26) which is coincident with the energetic threshold for reaction (2). The magnitudes of the self‐relaxation rate constants for O2(X³Σg−, v=26 and 27) are quantitatively consistent with the kinetic parameters of reaction (2). Relaxation by N2, while important for lower O2 vibrational states, is shown to be about 10 and 200 times slower than self relaxation for v=26 and v=27, respectively. These are the first two vibrational states of O2 that could form O3 via reaction (2).

Vibrational-state-specific total-removal relaxation rate constants, kv(M), for O2(X 3Σ−g, v=15 to 26) by M=CO2, N2O, and N2 have been obtained using the stimulated emission pumping (SEP) method in a pump–dump and probe configuration. Relaxation by O3 was studied using the chemical activation method, where the reaction: O(3P)+O3→O2(v)+O2, was employed to produce highly vibrationally excited O2 in an excess of ozone. Efficient (1%–2% of the gas kinetic limit) near-resonant 2–1 and/or 1–1 vibration-to-vibration (V–V) energy exchange was observed whenever the energy resonant condition was fulfilled and the transition in the quench partner would have been an allowed infrared transition in the isolated molecule. For M=CO2 and N2O, the temperature dependence of the 2–1 near-resonant energy transfer rate constants was found to be inverted. In contrast, the temperature dependence of the V–R, T relaxation rate constants for M=O2 was normal. For M=N2, a weak but positive temperature dependence was found. By extrapolating the temperature dependence to mesospheric temperatures (200 K) the effect of highly vibrationally excited O2 on the thermal budget can be discussed. The rate constant for the reaction of O(3P)+O3 was determined for an elevated collision energy of ∼10 kcal/mol and was found to be 5000 times larger than the room temperature rate constant.