High Resolution VUV Spectroscopy of Electron Impact Induced Emissions from Molecular Nitrogen

Emissions in the VUV have been probed for transitions from the Rydberg states (c4^{'} ^{1}Σu+ and b^{'} ^{1}Σu+) to the ground state (X ^{1}Σg+) in molecular nitrogen. The experimental setup consists of a 3m spectrometer and an electron collision chamber. The electron beam (with energy spread of ~0.5eV) was magnetically collimated with an axially symmetric magnetic field of ~100G 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 (i.e., N2 and H2) were dispersed by the spectrometer and detected at the rotationally-resolved level with a channel electron multiplier coated with CsI. Measured c4^{'} ^{1}Σu+ → X ^{1}Σg+ transition moment and predissociation yield of the c4^{'}(v^{'}=0) will be presented.

Acknowledgement: This work was carried out at JPL, Caltech, and SET under contracts with NASA and NSF. This research was performed while CPM held a NASA Postdoctoral Fellowship at JPL.