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

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 O 2 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 O 2 (X³Σ g − ,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 O 2 and N 2 at 295K. Self‐relaxation shows a sharp threshold for enhanced relaxation near the energy of O 2 (X³Σ g − , v=26) which is coincident with the energetic threshold for reaction (2). The magnitudes of the self‐relaxation rate constants for O 2 (X³Σ g − , v=26 and 27) are quantitatively consistent with the kinetic parameters of reaction (2). Relaxation by N 2 , while important for lower O 2 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 O 2 that could form O 3 via reaction (2).