In this poster, we describe our computational contributions to a joint theory-experiment study of atmospherically relevant photochemical processes involving nitrogen monoxide (NO). One aspect of this work involves the photodissociation of nitrosothiobenzene at 355 nm to produce NO and thiophenoxy. Experimental analysis of this process using velocity map imaging reveals two distinct dissociation pathways, corresponding to different final electronic states of the thiophenoxy radical. We use multireference methods (CASSCF and MSQDPT2 in the GAMESS package) to determine the two photodissociation mechanisms by analyzing the the energetics of dissociation on the ground and excited electronic states as well as the possible pathways between the electronic states through conical intersections and minimum energy crossing points. A second aspect of this work involves studying inelastic collisions between electronically excited NO in the A2Σ+ state and ground state O2. Specifically, we use multireference methods to determine the relative energetics of reactive collisions to form NO2 and O as well as ineleastic collisions resulting in non-radiative electronic relaxation. Our computational results will be compared with experimental velocity map imaging analysis of the various inelastic collision processes. This latter study has additional implications in combustion chemistry, where the laser induced fluorescence of NO is commonly used as a diagnostic of the conditions inside combustion engines. The quenching of excited NO through inelastic conditions with other gas molecules such as O2 will necessarily affect the interpretation of the fluorescence signal in such diagnostics.

Studying atmospherically relevant photochemical processes involving NO using multireference computational methods

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.