Reaction dynamics of ozone with unsaturated organic surfaces: Energy exchange, accomodation, and direct reactions


Reactions of O 3 with particulates and aerosols at the air-surface interface affect the balance of pollutants throughout the troposphere. Determining the interfacial reaction probabilities and mechanisms is critical to developing a comprehensive understanding of atmospheric heterogeneous chemistry. Molecular beam scattering of O 3 from the surface of well-ordered vinyl-terminated self-assembled monolayers has revealed that oxidation of the double bond depends significantly on the translational energy of O 3. For energies near room temperature, 5 kJ/mol, the initial reaction probability (γ 0) for the formation of the primary ozonide was determined to be γ 0 = 1.1 × 10 -5. As translational energy increases to 20 kJ/mol, the reaction probability decreases by a factor of two. This behavior, along with a strong inverse relationship between γ 0 and surface temperature, verifies that the room-temperature reaction follows the Langmuir-Hinshelwood mechanism, requiring accommodation prior to reaction. However, measurements show that the dynamics transition to a direct reaction for elevated translational energies. These insights may lead to the development of more accurate models for understanding the mechanistic and energetic details of interfacial O 3 reactions. Ultimately, this understanding will lead to more accurate simulations for predicting the fate and lifetime of O 3 in the environment.

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ACS National Meeting Book of Abstracts

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