Laboratory evidence for a possible non‐LTE mechanism of stratospheric ozone formation

Abstract

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).

Reactivity and electronic states of O4 along minimum energy paths

“…Another source of interest is the possible relevance of highly vibrationally excited states in determining the chemical composition of the atmosphere. This issue has been the subject of great interest and debate recently, [2][3][4][5][6][7][8][9] particularly in relation to the possibility of producing ozone from highly vibrationally excited O 2 molecules and considering that highly vibrationally excited O 2 molecules are known to be formed during the photodissociation of ozone in its triplet channel: 3,5 …”

Dynamics Study of the OH + O2Branching Atmospheric Reaction. 4. Influence of Vibrational Relaxation in Collisions Involving Highly Excited Species

“…5,10,[22][23][24] Following this idea, other sources of ozone, considering LTD conditions, have been suggested. For example, Wodtke and co-workers 5,[25][26][27][28] proposed an ozone source with basis on the reaction of vibrationally excited O 2 (V′′ g 26) with ground state O 2 , hereafter referred to as the "Wodtke mechanism"…”

Dynamics Study of the O2 + HO2 Atmospheric Reaction with Both Reactants Highly Vibrationally Excited

“…The energy dependence holds important information about the behavior of molecules at high energies and can provide clues as to the microscopic details of intermolecular energy transfer. 6 Vibrationally excited molecular oxygen [hereafter denoted by O 2 (V)], generated in the ultraviolet photolysis of ozone, has recently been proposed [7][8][9][10] to explain the limitations of traditional atmospheric ozone models. [11][12][13] In fact, models of atmospheric chemistry have consistently underpredicted the measured ozone concentrations in the upper stratosphere and mesosphere in recent years.…”