CEDAR: RUI--Quenching of Vibrationally-Excited Ozone by Atomic Oxygen

Bucknell University, Lewisburg PA

Investigators

Abstract

This is a 3-year project is to conduct laboratory measurements of the relaxation rate coefficients for the lowest three vibration levels of ozone in collisions with ground-state oxygen atoms. These are critical parameters in the modeling of ozone remote sensing data and retrieval of its mesospheric density. Two independent experimental methods will be employed. In the first approach, a fraction of ozone is photo-dissociated by a 266-nm laser pulse, generating atomic oxygen and causing a temperature jump. The populations in the excited (010) and (001) vibration levels will be monitored using transient diode laser absorption spectroscopy as they equilibrate, providing information on the corresponding relaxation rate coefficients. To avoid complications from the temperature-jump approach, the second approach will involve direct pumping of the (001) vibration with a pulsed IR laser to produce vibrationally excited ozone. After performing experiments at room temperature, temperature dependence of the rate coefficients in the 150-350 K range, which is more relevant to the upper mesosphere and lower thermosphere region, will be studied. The broader impacts of the project are substantial. First, undergraduate students will be involved in every aspect of the proposed research project, including experimental design, data collection, signal processing, electronics and computer interfacing, data analysis, kinetic modeling, and dissemination of results at local symposia and regional or national scientific meetings. In addition to laboratory experiences at Bucknell University, the students will be engaged in data analysis and kinetic modeling activities at the AFRL hanscom AFB through the collaboration that has already been established between these two groups. In this, the proposal offers unique and excellent opportunities for undergraduate student research experiences. Second, the methods and results have general utility within atmospheric chemistry and ozone research and will lead to greatly improved capabilities to track long term variations in climate.