Gas-Surface Interactions Near Dissociation Threshold
Abstract
Our earlier studies of molecule-surface CID were extended to the case of NO2, which has been implicated as the emitting species in shuttle glow phenomena. The glow is believed to derive from the recombination of NO and atomic oxygen, yielding internally excited NO2. Because the NO2 zeroth order 2B2 excited state is strongly coupled to the 2A1 ground state, levels formed in recombination reactions emit throughout the visible. In our experiments, the reverse process was examined. Namely, NO2 entrained in a molecular beam was directed at a crystal surface and was photoexcited 2 cm (10 ms) before reaching the surface. The incident molecules had enough internal plus translational energy to undergo CID, which was observed for a range of NO2 internal excitations. Unexcited NO2 yielded no signal. Additionally, NO was detected with state and angular resolution and it was shown that products were scattered preferentially in the specular direction, ruling out a long residence time on the surface. It is most likely that NO2 decomposes rapidly following impact with the surface, in accord with k(E) measurements that indicate subpicosecond lifetimes for excess energies - 500 cm. This was the first demonstration of such an effect and supports the thesis that NO2 is responsible for the shuttle glow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1994
- Accession Number
- ADA284945
Entities
People
- Curt Wittig
- Hanna Reisler
Organizations
- University of Southern California