The reactivity and hydration properties of amorphous carbon were studied in a low-pressure Knudsen cell reactor at room temperature (298 K). Reactions of NO 2 (y = 0.11 + 0.04) and HNO 3 (y = 0.038 + 0.008) were observed and may be important for nitrogen partitioning in the atmosphere. Water uptake was measured before and after exposure to various gases. Treating the amorphous carbon with NO 2 and 03 does not alter the H20 uptake, while treatment with SO 2, HNO3, and H2SO 4 significantly increases the H20 uptake. The experimental results support current assumptions in jet aircraft plume models that sulfuric acid condensation is involved in the activation of soot particles as condensation nuclei.

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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).

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