Electron impact excitation of atomic oxygen.

A composite beam of atomic and molecular oxygen was generated using a microwave cavity and special gas handling surfaces to minimize O recombination. Further, a magnetically constrained electron beam of well-known energy was used to excite the oxygen gas target. The resulting fluorescence was probed using a 0.2m vacuum monochromator and a CsI-coated channel electron multiplier. Spectral scans (intensity as a function of wavelength with fixed impact energy) and excitation function scans (intensity as a function of impact energy for a wavelength interval) were used to quantify the VUV emissions of atomic oxygen. The monitored dissociation fraction and known 130.4nm atomic oxygen emission cross section [Johnson et al., Can. J. Phys. 83, 589-616 (2005)] were used for normalization of the measured excitation functions. Resulting VUV emission cross sections of atomic oxygen via electron impact will be presented.