| 1. |
- Feifel, Raimund, et al.
(författare)
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From localised to delocalised electronic states in free Ar, Kr and Xe clusters
- 2004
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 30:3, s. 343-351
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Tidskriftsartikel (refereegranskat)abstract
- We present new results for the inner valence levels of clusters of the three inert gases Ar, Kr and Xe based on photoelectron spectroscopy studies. The inner valence levels are compared to the localised core levels and to the delocalised outer valence levels. This comparison shows a gradual change from a relatively localised behaviour for Ar inner valence 3s, over the intermediate case of Kr inner valence 4s, to a more delocalised behaviour for Xe inner valence 5s. This change correlates well with the ratio between the orbital sizes and the interatomic distances. The Kr4s intermediate case is found to exhibit characteristics of both localised and delocalised behaviour.
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| 2. |
- Lundwall, M, et al.
(författare)
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Radial surface segregation in free heterogeneous argon/krypton clusters
- 2004
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 392:4-6, s. 433-438
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Tidskriftsartikel (refereegranskat)abstract
- Free clusters produced by a co-expansion of argon and krypton have been studied by means of core level photoelectron spectroscopy. In this study we have determined: (i) the produced clusters are heterogeneous; (ii) the radial distribution of the two atomic species in the cluster differs. The proposed structure model places the majority of the krypton atoms in the bulk, leaving the argon atoms to be found more frequently on the cluster surface. The suggested structure is qualitatively discussed using the cohesive energies of the two-components. (C) 2004 Elsevier B.V. All rights reserved.
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| 3. |
- Ohrwall, G, et al.
(författare)
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Femtosecond interatomic Coulombic decay in free neon clusters: Large lifetime differences between surface and bulk
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:17
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative determination of 2s vacancy lifetimes in surface and bulk atoms of free Ne clusters has been made. While for free atoms the 2s inner-valence hole has a ps lifetime, it reduces to 6+/-1 fs for cluster bulk atoms. For surface atoms, the lifetime is on average longer than 30 fs. The lifetime estimate was obtained from fits of high-resolution photoelectron spectra of Ne clusters. The shortening of the lifetime is attributed to the coordination dependent interatomic Coulombic decay, which is extremely sensitive to internuclear distances.
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| 4. |
- Ohrwall, G, et al.
(författare)
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Observation of elastic scattering effects on photoelectron angular distributions in free Xe clusters
- 2003
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36:19, s. 3937-3949
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Tidskriftsartikel (refereegranskat)abstract
- We report an observation of substantial deviations in the photoelectron angular distribution for photoionization of atoms in free Xe clusters compared to the case of photoionization of free atoms. The cross section, however, seems not to vary between the cluster and free atoms. This observation was made in the vicinity of the Xe 4d Cooper minimum, where the atomic angular distribution is known to vary dramatically. The angular distribution of electrons emitted from atoms in the clusters is more isotropic than that of free atoms over the entire kinetic energy range studied. Furthermore, the angular distribution is more isotropic for atoms in the interior of the clusters than for atoms at the surface. We attribute this deviation to elastic scattering of the outgoing photoelectrons. We have investigated two average cluster sizes, (N) approximate to 4000 and 1000 and found no significant differences between these two cases.
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| 5. |
- Tchaplyguine, Maxim, et al.
(författare)
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Selective probing of the electronic structure of free clusters using resonant core-level spectroscopy
- 2003
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Ingår i: Chemical Physics. - 0301-0104. ; 289:1, s. 3-13
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the first resonant photoemission and partial electron yield studies of free clusters are presented. The resonant photoemission spectra of free argon clusters have been recorded with excitation energies determined from the cluster X-ray absorption spectrum near the Ar 2p ionization threshold. The decay of 2p(-1)4s and 2p(-1)3d cluster surface and "bulk" excited states has been investigated in detail. The combination of resonant photoemission and partial electron yield methods has allowed a selective probing of the electronic and geometric structure, yielding new results concerning the interplay between the energy of the excited states, their orbital character and the local atomic coordination. These new results demonstrate the power of resonant core level spectroscopy when applied to free clusters, as well as the advantages of free clusters for the studies of the bulk and surface energetics of nanoscale solids. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 6. |
- Tchaplyguine, Maxim, et al.
(författare)
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The size of neutral free clusters as manifested in the relative bulk-to-surface intensity in core level photoelectron spectroscopy
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:1, s. 345-356
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Tidskriftsartikel (refereegranskat)abstract
- A new approach for obtaining an estimate of the effective size of the free neutral clusters is proposed. The approach relies on an experimental measure of the surface and interior or "bulk" cluster atoms provided by the x-ray photoelectron spectroscopy and on a model for the attenuation of photoelectrons ejected from the bulk of the cluster as the result of the ionizing irradiation. The experimental part gives the ratio of the electron signal from the bulk cluster atoms to that from the cluster surface atoms for a wide range of cluster sizes and electron kinetic energies. The attenuated response of the bulk atoms is modeled using an exponential law with the cluster size and kinetic-energy-dependent electron escape depth as parameters. For the experimental size range, model-based calculations for Ar, Kr, and Xe clusters are presented. The cluster size estimates obtained from comparison of the model calculations and experimental results agree well with those determined from the parameters of the cluster creation process. The combination of experiment and modeling also makes it possible to estimate the effective escape depth for electron propagation in free clusters. For Ar, Kr, and Xe clusters of varying mean size, absolute determination of the surface and bulk electron binding energies of the core levels used in the experiments has also been made. (C) 2004 American Institute of Physics.
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| 7. |
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| 8. |
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| 9. |
- Tchaplyguine, Maxim, et al.
(författare)
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Variable surface composition and radial interface formation in self-assembled free, mixed Ar/Xe clusters
- 2004
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 69:3
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Tidskriftsartikel (refereegranskat)abstract
- Using photoelectron spectroscopy, we demonstrate how the self-assembling process of cluster formation in an adiabatic expansion leads to radial segregation and layering as well as to variable surface composition for binary Ar/Xe clusters. The radial structuring can be qualitatively understood from the different interatomic bonding strengths of the two components.
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| 10. |
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