Collective migration of adsorbed atoms on a solid surface in the laser radiation field

Андреев, В. В.; Ignat'ev, D V; Telegin, G. G.

doi:10.1070/qe2004v034n02abeh002596

Cited by 3 publications

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“…Successive photostimulated assembly of clusters adsorbed on the surface of various solid-state systems is one method for synthesizing nanostructures with sizes and properties determined beforehand [1][2][3][4][5][6][7][8]. The formation of clusters containing few atoms from adsorbed atoms and subsequent enlargement of the clusters necessitate that the size of the centers be controlled over the whole assembly process.…”

Section: Introductionmentioning

confidence: 99%

Photoionization spectra of silver dimers adsorbed on the surface of a ZnS single crystal

et al. 2007

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We use the photostimulated luminescence flash method to measure photoionization spectra of Ag 2 clusters adsorbed on the surface of a ZnS single crystal. Adsorbed dimers of silver are prepared by treatment of the surface of a ZnS single crystal in high vacuum with a beam of molecular Ag 2 + ions followed by their neutralization. We show that the adsorbed dimers create two types of electron traps at energy levels 1.63 and 1.82 eV below the bottom of the conduction band.

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Section: Introductionmentioning

confidence: 99%

Photoionization spectra of silver dimers adsorbed on the surface of a ZnS single crystal

et al. 2007

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Photoionization spectra of silver atoms adsorbed on the surface of a ZnS single crystal

et al. 2006

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We have used photostimulated flash luminescence to study deep electronic states arising when silver ions Ag + are deposited under high vacuum onto the surface of a ZnS single crystal, followed by creation of the conditions for neutralization of the silver ions. The flux density of the silver ion beam was 10 7 cm -2 ⋅sec -1 . We have observed the appearance of two types of deep electronic states with photoionization energies 1.60 eV and 1.80 eV, arising after depositing the silver ions onto the surface of the ZnS single crystal. We have hypothesized that there may be two different preferred sites for adsorption of silver atoms on the zinc sulfide surface. The corresponding photoionization spectra of the adsorbed silver atoms have maxima at 775 nm and 690 nm.Key words: adsorbed silver atom, zinc sulfide, photoionization spectrum, photostimulated flash luminescence. Introduction.Today there is considerable interest in development of modern methods and principles for making nanoparticles and nanostructures. Such problems are relatively easy to solve, for example, for molecules when their capacity for self-organization is utilized, and for small atomic clusters and nanoparticles that can be prepared during chemical synthesis and incorporated into foreign matrices and porous structures [1][2][3][4][5]. A number of papers (see, for example, [6-8]) demonstrate the possibility of sequential photostimulated assembly of adsorbed nanoparticles from atoms and small atomic clusters. During such investigations, there are problems involved in obtaining individual, noninteracting atoms and monodisperse small atomic clusters adsorbed on the surface of real ionic/covalent crystals. However, so far in most cases the optical and other properties are still unknown for atoms and small atomic clusters of a strictly determined size that are adsorbed on the surface of crystals. Such problems can be solved only when these centers are present on the real crystal surface in concentrations ruling out their pairwise interaction and their joining into systems of another size, and making up at least 10 -3 to 10 -6 of the monolayer. However, sometimes it is simply impossible to observe such low concentrations of adsorbed centers using standard procedures. Some success has been achieved by using luminescence techniques such as photostimulated flash luminescence, for example [9,10]. Such problems have been successfully solved for atoms and clusters of a metal by itself, in particular silver on the surface of silver chloride [11,12]. This work has been devoted to studies of the spectral properties of individual silver atoms adsorbed on the surface of a ZnS crystal. We have not encountered similar research in the scientific literature. We also know that deep electronic states appear upon adsorption of silver particles of atomic or molecular dispersity on the surface of zinc sulfide crystals [13]. The practical use of such deep electron traps is certainly promising (see, for example, [14]).We obtained the photoionization spectra of adsorbed silver ato...

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Enhancement of the Catalytic Performances in the Case of a Consecutive-Parallel Reaction Scheme

Benguerba¹,

Djellouli²

2010

International Journal of Chemical Reactor Engineering

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The determination of the optimal distribution of the catalytic activity profile, which maximizes the catalytic effectiveness and the selectivity, in created unsteady state conditions, is analyzed and treated numerically for the case of a consecutive-parallel reaction scheme. The optimal active element distribution is always a Dirac-? function, i.e., all the catalyst is deposited at a specific distance from the center of the catalytic pellet. The main result is that the location of this optimal position varies with time and that the modulation, of the temperature and the reactants concentrations of the external bulk fluid, leads to a considerable increase of the catalytic effectiveness. On the other hand the selectivity was found to be not affected by the modulation except for higher values of ?2 (?2>0.3).

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Collective migration of adsorbed atoms on a solid surface in the laser radiation field

Cited by 3 publications

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Photoionization spectra of silver dimers adsorbed on the surface of a ZnS single crystal

Photoionization spectra of silver dimers adsorbed on the surface of a ZnS single crystal

Photoionization spectra of silver atoms adsorbed on the surface of a ZnS single crystal

Enhancement of the Catalytic Performances in the Case of a Consecutive-Parallel Reaction Scheme

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