Metastable Oxygen Production by Electron-Impact of Oxygen

Electron-impact excitation processes involving atomic and molecular oxygen are important in atmospheric interactions. The production of long-lived metastable O(¹S) and O(¹D) through electron impact of oxygen-containing molecules plays a significant role in the dynamics of planetary atmospheres (Earth, Mars, Europa, Io, Enceladus) and cometary bodies (Hale-Bopp). The electron-impact excitation channels to O(¹S) and O(¹D) are important for determining energy partitioning and dynamics. To reliably model natural phenomena and interpret observational data, the accurate determination of underlying collision processes (cross sections, dissociation dynamics) through fundamental experimental studies is essential. The detection of metastable species in laboratory experiments requires a novel approach. Typical radiative de-excitation detection techniques cannot be performed due to the long-lived nature of excited species, and conventional particle detectors are insensitive to the low internal energies O(¹S) and O(¹D). We have recently constructed an apparatus to detect and characterize metastable oxygen production by electron impact using the "rare gas conversion technique." Recent results will be presented, including absolute excitation functions for target gases O₂, CO, CO₂, and N₂O. This work was performed at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). Financial support through NASA's OPR, PATM, and MFRP programs, as well as the NASA Postdoctoral Program (NPP) are gratefully acknowledged.