Physisorption Kinetics

Kreuzer, H. J.; Gortel, Zbigniew W.

doi:10.1007/978-3-642-82695-5

Cited by 78 publications

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“…Since the enthalpies of adsorption for the noble gases are essentially zero [5], the average distance traveled per particle, L, through the target/vapor transport system can be determined from Eq. 2.…”

Section: Discussionmentioning

confidence: 99%

A Universal Method For Effusive-Flow Characterization of Target/Vapor Transport Systems For RIB Generation

Bilheux¹,

Alton²,

Liu³

et al. 2003

AIP Conference Proceedings

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Worldwide interest in the use of accelerated radioactive ion beams (RIBs) for exploring reactions important in understanding the structure of the nucleus and nuclear astrophysical phenomena has motivated the construction of facilities dedicated to their production and acceleration. Many facilities utilize the Isotope-Separator-On-Line (ISOL) method in which species of interest are generated within a solid or liquid target matrix. Experimentally useful RIBs are often difficult to generate by this technique because of the times required for diffusion from the interior of the target material, and to effusively transport the species of interest to the ion source following diffusion release in relation to its lifetime. Therefore, these delay times must be minimized. We have developed an experimental method that can be used to determine effusive-flow times of arbitrary geometry target/vapor transport systems. The technique utilizes a fast valve to measure effusive-flow times as short as 0.1 ms for any chemically active or inactive species through any target system, independent of size, geometry and materials of construction. In this report, we describe the effusive-flow experimental arrangement and provide time spectra for noble gases through prototype RIB target/vapor-transport systems.

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Section: Discussionmentioning

confidence: 99%

A Universal Method For Effusive-Flow Characterization of Target/Vapor Transport Systems For RIB Generation

Bilheux¹,

Alton²,

Liu³

et al. 2003

AIP Conference Proceedings

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“…Below, we sketch a quantum-kinetic approach to calculate s e and τ e from a simple microscopic model for the plasma boundary interaction which treats the interaction of electrons with plasma boundaries as a physisorption process [30,31,32,33,34,35,36,37,38,39,40] in the polarization-induced attractive part of the surface potential. Electron surface states [41,42,43,44,45,46,47,48,49,50,51,52,53,54,55], at most a few nm away from the boundary, will thus play a central role as will surfacebound scattering processes which control electron energy relaxation at the surface and thus electron sticking and desorption.…”

Section: −1 Imentioning

confidence: 99%

“…Usually, heavy particles, such as ions, couple rather strongly to vibrational excitations of the boundary [36,39]. They can thus dissipate energy very efficiently which usually leads to a large sticking coefficient.…”

mentioning

confidence: 99%

“…For an electron to get stuck at (to desorb from) a surface it has to loose (gain) energy at (from) the surface [36]. This can only occur through inelastic scattering with the grain surface.…”

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confidence: 99%

“…where h is Planck's constant, T s is the surface temperature, and E d e is the electron desorption energy, that is, the binding energy of the surface state from which desorption most likely occurs [36]. The great virtue of this equation is that it relates a combination of kinetic coefficients, which depend on the details of the inelastic (dynamic) interaction, to an energy, which can be deduced from the static interaction alone.…”

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Physisorption kinetics of electrons at plasma boundaries

2009

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Abstract. Plasma-boundaries floating in an ionized gas are usually negatively charged. They accumulate electrons more efficiently than ions leading to the formation of a quasi-stationary electron film at the boundaries. We propose to interpret the build-up of surface charges at inert plasma boundaries, where other surface modifications, for instance, implantation of particles and reconstruction or destruction of the surface due to impact of high energy particles can be neglected, as a physisorption process in front of the wall. The electron sticking coefficient se and the electron desorption time τe, which play an important role in determining the quasi-stationary surface charge, and about which little is empirically and theoretically known, can then be calculated from microscopic models for the electron-wall interaction. Irrespective of the sophistication of the models, the static part of the electron-wall interaction determines the binding energy of the electron, whereas inelastic processes at the wall determine se and τe. As an illustration, we calculate se and τe for a metal, using the simplest model in which the static part of the electron-metal interaction is approximated by the classical image potential. Assuming electrons from the plasma to loose (gain) energy at the surface by creating (annihilating) electron-hole pairs in the metal, which is treated as a jellium half-space with an infinitely high workfunction, we obtain se ≈ 10 −4 and τe ≈ 10 −2 s. The product seτe ≈ 10 −6 s has the order of magnitude expected from our earlier results for the charge of dust particles in a plasma but individually se is unexpectedly small and τe is somewhat large. The former is a consequence of the small matrix elements occurring in the simple model while the latter is due to the large binding energy of the electron. More sophisticated theoretical investigations, but also experimental support, are clearly needed because if se is indeed as small as our exploratory calculation suggests, it would have severe consequences for the understanding of the formation of surface charges at plasma boundaries. To identify what we believe are key issues of the electronic microphysics at inert plasma boundaries and to inspire other groups to join us on our journey is the purpose of this colloquial presentation.PACS. 52.27.Lw Dusty or complex plasmas -52.40.Hf Plasma-material interaction, boundary layer effects -68.43.-h Chemi-/Physisorption: adsorbates on surfaces -73.20.-r Electron states at surfaces and interfaces

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Dynamics of propene metathesis: Physisorption and diffusion in heterogeneous catalysis

Gomes

Fuller

1996

AIChE Journal

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Physisorption Kinetics

Cited by 78 publications

References 0 publications

A Universal Method For Effusive-Flow Characterization of Target/Vapor Transport Systems For RIB Generation

A Universal Method For Effusive-Flow Characterization of Target/Vapor Transport Systems For RIB Generation

Physisorption kinetics of electrons at plasma boundaries

Dynamics of propene metathesis: Physisorption and diffusion in heterogeneous catalysis

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