Photochemical Measurements of Virtual Atmospheres

Sri International, Menlo Park CA

Investigators

Abstract

The project will undertake laboratory reactor experiments that seek to recreate the photochemistry of the upper atmosphere in order to solve existing dilemmas regarding the modeling and understanding of recent and new atmospheric measurements. Although lower pressures and longer times pertain to the real atmosphere, computer modeling we can be used to design the virtual atmosphere experiments so that they are sensitive to the same chemistry and photolysis. The chemistry of the upper stratosphere and mesosphere to be explored by the study is dominated by reactive oxygen- and hydrogen-containing species, many of which we will measure with great sensitivity and selectivity using a series of laser diagnostics. This concept will provide a new technique to validate our understanding of the photochemistry of hard-to-access regions and uncover any unknown features. The experiments will be conducted in a large reactor bulb with quantified inlet and outlet flows of oxygen, nitrogen, ozone, and water, operating near 1 torr with 3- to 6-minute residence times, and subject to ultraviolet photolysis with well-characterized lamp or laser radiation. The appropriate operating conditions and diagnostics will be combined to address specific topics of current interest, debate, or measurement activity, including the failure of current mesospheric models to predict observed OH and HO2 levels, and the role of excited oxygen and hydroxyl states in the heating, signatures, and chemistry of the upper atmosphere.