Electron Impact Induced VUV Emissions from Atmospheric Gases

Emissions in the VUV have been probed for transitions from various excited electronic states (e.g., N^{\ast} (3s 4P)) resulting from electron impact of various atmospheric gases, including nitrous oxide (N2O). The experimental setup consists of a 0.2m spectrometer and an electron collision chamber. The electron beam (with energy spread of ~0.5eV) was magnetically collimated with an axially symmetric magnetic field and accelerated to a given kinetic energy. A Faraday cup was used to monitor the beam current and to minimize the back-scattered electrons. Photons emitted by electron impact excited target molecules and excited atoms following dissociative excitation, were dispersed by the spectrometer and detected with a channel electron multiplier coated with CsI. Measured emission spectra and emission cross sections as functions of incident energy will be presented.

Acknowledgement: This work was carried out at JPL, Caltech, under contracts with NASA and NSF. This research was performed while CPM and JWMcC held NASA Fellowships at JPL.