ABSTRACT

This project will undertake detailed investigations of hydroxyl and nitric oxide chemistry in the upper atmosphere. The reaction between hydrogen atoms and ozone produces OH with up to nine quanta of vibrational excitation. The excited vibrational levels are quenched predominantly by collisions with O and O2. Rate coefficients for quenching of OH vibrational levels v = 1 - 5 by collisions with O atoms and levels v = 1 - 9 by collisions with O2 molecules at temperatures of interest in the mesosphere will be determined using accurate quantum and semiclassical calculations. The resulting database of vibrational relaxation rate coefficients will be made available over the world-wide web. Nitric oxide is the key radiating species in the lower thermosphere and it is produced in highly rotationally and vibrationally excited levels by the reaction between O2 and nitrogen atoms in the ground and electronically excited states. Through quantum scattering calculations on accurate molecular potentials, the proposed work will provide the rate of production of nitric oxide in specific vibrational and rotational levels as functions of the altitude in the thermosphere. Collisional excitation of NO by atomic oxygen and its subsequent deexcitation through collisions with O atoms will also be undertaken using quantum mechanical approaches to quantitatively describe the NO fundamental vibration-rotation band emission at 5.3 - m. The results can be used in models of the energy balance and chemical structure of the upper atmosphere. The broader impacts of the project includes its applicability to a number of middle atmosphere science topics. The research will provide rate coefficients for key reactions in aeronomic models of the mesospheric and lower thermospheric energy budget. As part of the educational component, the project will train a Ph. D. level graduate student and two or three undergraduate students in atmospheric chemistry. Preference will be given to candidates from under-represented communities. The project will also support a postdoctoral scholar who will be responsible for a large portion of the project.

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