24 research outputs found
Classification of Light-Induced Desorption of Alkali Atoms in Glass Cells Used in Atomic Physics Experiments
We attempt to provide physical interpretations of light-induced desorption
phenomena that have recently been observed for alkali atoms on glass surfaces
of alkali vapor cells used in atomic physics experiments. We find that the
observed desorption phenomena are closely related to recent studies in surface
science, and can probably be understood in the context of these results. If
classified in terms of the photon-energy dependence, the coverage and the
bonding state of the alkali adsorbates, the phenomena fall into two categories:
It appears very likely that the neutralization of isolated ionic adsorbates by
photo-excited electron transfer from the substrate is the origin of the
desorption induced by ultraviolet light in ultrahigh vacuum cells. The
desorption observed in low temperature cells, on the other hand, which is
resonantly dependent on photon energy in the visible light range, is quite
similar to light-induced desorption stimulated by localized electronic
excitation on metallic aggregates. More detailed studies of light-induced
desorption events from surfaces well characterized with respect to alkali
coverage-dependent ionicity and aggregate morphology appear highly desirable
for the development of more efficient alkali atom sources suitable to improve a
variety of atomic physics experiments.Comment: 6 pages, 1 figure; minor corrections made, published in e-Journal of
Surface Science and Nanotechnology at
http://www.jstage.jst.go.jp/article/ejssnt/4/0/4_63/_articl
H2S Adsaorption on Polycrystalline UO2.
Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe
The Interactions of Thiophene with Polycrystalline UO2.
Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe
Energy Distributions for Desorption of Sodium and Potassium from Ice: The Na/K Ratio at Europa
International audienceThe sputtering and decomposition of the surface of Europa by fast ions and electrons lead to the production of an atomosphere containing sodium and potassium atoms. Here time-of-flight energy distributions are measured for Na and K sputtered from a vapor-deposited ice by 200-eV electrons. These data are then used in a Monte Carlo simulation for alkalis in Europa's atmosphere. Na/K ratios versus distance from Europa are calculated and compared to the recent observations in the range 6 to 18 Europan radii from the surface. Normalizing to the observations, the Na/K ratio for the loss rates is ∼27 and the ratio for the average surface source rates is ∼20. These ratios are very different from the Na/K ratio at Io and are larger than the Na/K ratio suggested for Europa's putative subsurface ocean, consistent with fractionation on freezing and upwelling of ocean material
Theoretical modeling of photon and electron-stimulated Na and K desorption from SiO2
The mechanism of generation of atomic Na and K from SiO2 samples has been studied using explicitly correlated wave function and density functional theory cluster calculations. Possible pathways for the photon and electron stimulated desorption of Na and K atoms from silicates are proposed, thus providing new insight on the generation of the tenuous Na and K atmosphere of the Moon