UV photon and low-energy (5--150 eV) electron-stimulated processes at environmental interfaces
- Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.
Irradiation of surfaces and interfaces with low-energy (5--150 eV) electrons and ultraviolet photons occurs during the storage of ``mixed`` (chemical/radioactive) waste forms and during processing steps which involve the use of low temperature plasmas. It is well known that electron- and photon-stimulated desorption (ESD and PSD) from wide band-gap materials and interfaces can be initiated by Auger decay of deep valence and shallow core holes. This process consists of hole production, Auger decay, reversal of the Madelung potential, and ion expulsion due to the Coulomb repulsion. ESD and PSD of neutrals also occurs and involves production of electron-hole pairs and excitons. Generally, neutral yields dominate ESD and PSD cross sections, which typically vary between {approximately}10{sup {minus}16} and 10{sup {minus}22} cm{sup 2}. The authors present results on the ESD and PSD of environmentally relevant substrates such as ZrO{sub 2}(100), soda-glass, and NaNO{sub 3}. The major cation thresholds and yields indicate that ESD and PSD from these complex materials involves Auger stimulated events. In particular, desorption thresholds correlate with ionization of the O(2s), Zr(4p), Si(2p) and Na(2s) levels. The near band-gap threshold energy ({approximately}5--7 eV) for the desorption of neutrals (i.e., atomic oxygen, NO, etc) demonstrate the overall importance of self-trapped and localized excitons in both ESD and PSD of typical ceramics and oxides.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 338489
- Report Number(s):
- CONF-970559--
- Country of Publication:
- United States
- Language:
- English
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