| 1. |
- Andersson, Tomas, et al.
(författare)
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Photon energy influence on valence photoelectron spectra of silver clusters
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:15, s. 152028-
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Tidskriftsartikel (refereegranskat)abstract
- Silver clusters in the size range of ∼102 constituent atoms have been studied using photoelectron spec-troscopy. The 5s and 4d valence bands have been probed with 40 and 60.5 eV photon energies. Differences in the valence band spectral features have been observed and are discussed in view of earlier results on copper clusters and in terms of differences in mean free path for electrons of different energies.
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| 2. |
- Iablonskyi, D., et al.
(författare)
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High resolution study of the inner-shell 3p-3d and 3p-5s resonance regions in calcium atoms
- 2013
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 186, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- The 3p(5)4s(2)3d P-1(1) and 3p(5)(P-2(3/2))4s(2)5s (2)[3/2](1) resonance regions of Ca atoms have been studied experimentally with the aid of synchrotron radiation excited electron spectroscopy. The strong configuration interaction of the 3p(5)4s(2)3d, 3p(5)4s(2)5s and several other nearly degenerate configurations leads to complex structures observed in the photoelectron yield spectrum. Multiconfiguration Dirac-Fock (MCDF) calculations have been performed for these 3p-excited resonances of neutral calcium and compared to experimental results. The excitation and subsequent autoionization of these resonances lead to the final ionic 3p(6)nl states from which new high-lying members of the Rydberg p-series have been resolved experimentally. These new levels agree reasonably well with calculations as well as with the extrapolation of the Rydberg formula. The post collision interaction (PCI) effect has been observed in the transition Ca+ 3p(5)3d4s P-2(1/2,3/2)-> Ca2+ 3p(6) S-1(0) + e(Auger)(-) and explained by means of the rather long core-hole lifetime, while the decay of Ca+ 3p(5)3d4s P-4(1/2),(3/2,5/2) states is not affected by PCI. (c) 2013 Elsevier B.V. All rights reserved.
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| 3. |
- Jankala, K., et al.
(författare)
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Analysis of 3d photoionization and subsequent Auger decay of atomic germanium
- 2011
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 84:5
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Tidskriftsartikel (refereegranskat)abstract
- Experimental and theoretical study of the 3d photoionization and subsequent Auger decay of initially neutral atomic germanium is presented. The features of the high-resolution photoelectron and Auger electron spectra are interpreted with the aid of multiconfiguration calculations. The binding energies and relative cross sections of the 3d ionized fine-structure states of Ge are given. The complete M4,5NN Auger electron spectrum to doubly ionized final states of the Ge ion is interpreted and discussed.
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| 4. |
- Jankala, K., et al.
(författare)
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Photon Energy Dependent Valence Band Response of Metallic Nanoparticles
- 2011
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 107:18
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Tidskriftsartikel (refereegranskat)abstract
- We show that the valence band response to photon impact in metallic nanoparticles is highly energy dependent. This is seen as drastic variations of cross sections in valence photoionization of free and initially charge-neutral nanosized metal clusters. The effect is demonstrated in a combined experimental and theoretical study of Rb clusters. The experimental findings are interpreted theoretically using a jellium model and superatom description. The variations are attributed to the changing overlap with the photon energy between the wave functions of diffuse delocalized valence electrons and continuum electrons producing a series of minima in the cross section.
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| 5. |
- Kettunen, J. A., et al.
(författare)
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Electron-ion coincidence study of photofragmentation of the CdCl2 molecule
- 2011
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174. ; 46:9, s. 901-907
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the photofragmentation subsequent to valence and Cd4d photoionization of cadmium dichloride (CdCl2) were studied using He I and synchrotron excitation. The measurements were performed with a photoelectron-photoion coincidence (PEPICO) setup, and the connection between the singly ionized electronic states and cationic fragments was investigated. The valence-ionized states were found to lead to CdCl2+, Cd+ and CdCl+. The Cd4d(-1) states were found to lead only to Cl+ ions. The observed charge transfer effect between Cd and Cl was concluded to take place due to internal conversion or fluorescence decay to dissociating valence states either directly or through consecutive fragmentation. The fragmentation energetics were investigated with molecular ab initio calculations, and the calculated energies were found to agree with the detected fragment appearances. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 6. |
- Mikkela, M-H, et al.
(författare)
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Photoelectron spectroscopy of unsupported bismuth clusters: Size related effects of metallic properties
- 2012
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 112:8
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Tidskriftsartikel (refereegranskat)abstract
- Evolution of metallic properties of free and initially neutral nanoscale Bi clusters has been studied using synchrotron radiation excited photoelectron spectroscopy. The 4f and 5d core as well as the valence levels have been probed. The cross-level analysis indicates metallic properties in Bi clusters in the observed size range from 0.5 nm to 1.4 nm. The behavior of the core-level and valence binding energies as a function of cluster size has been observed to be smooth and relatively consistent. Valence responses for the largest clusters have their shape and width similar to those of the polycrystalline solid Bi. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759324]
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| 7. |
- Mikkela, M. -H., et al.
(författare)
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Size-dependent study of Rb and K clusters using core and valence level photoelectron spectroscopy
- 2011
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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. ; 64:2-3, s. 347-352
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Tidskriftsartikel (refereegranskat)abstract
- Electronic structure of free and neutral Rb and K clusters containing from few tens to few hundred atoms has been studied using synchrotron radiation. Core-level photoelectron spectroscopy has been used to probe the metallic nature of Rb and K clusters. We show that the metallicity exists down to the dimensions of few nanometers. Simultaneously the emergence and evolution of the valence band structure has been monitored by the valence-level photoelectron spectroscopy.
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| 8. |
- Osmekhin, S., et al.
(författare)
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Size-dependent transformation of energy structure in free tin clusters studied by photoelectron spectroscopy
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:2, s. 023203-
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Tidskriftsartikel (refereegranskat)abstract
- Free nanoscale tin clusters in the average size range of a few tens up to similar to 500 atoms are studied by means of valence and core-level photoelectron spectroscopy. A self-consistent picture arises from comparison of the work functions derived from the 4d core-level spectra, the experimental ionization energies extracted from the 5p valence spectra, and the expectations from the metallic sphere model for the clusters. The present studies demonstrate that the 4d core-level energy changes are a sensitive probe of the metal-to-semiconductor transition in the size range under investigation.
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| 9. |
- Patanen, M., et al.
(författare)
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Valence photoionization and photoelectron-photoion coincidence (PEPICO) study of molecular LiCl and Li2Cl2
- 2012
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 185:8-9, s. 285-293
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Tidskriftsartikel (refereegranskat)abstract
- Molecular LiCl and Li2Cl2 have been studied in the vapor phase with valence photoelectron and photoelectron-photoion coincidence spectroscopies. These two techniques determine the binding energies in fundamentally different ways. Binding energies obtained from photoelectron spectra are usually taken as the vertical ionization energies of the corresponding electronic states. In cases with several overlapping bands, corresponding to different electronic states, the coincidence measurement can separate the bands if the respective final states fragment differently. This applies well to the monomer case. To facilitate the determination of state-specific ionization energies in the dimeric molecule, a theoretical Franck-Condon analysis has been carried out. Moreover, ab initio coupled-cluster and density-functional-theory calculations have been used to analyze the fragmentation pattern based on asymptotic dissociation energies. The fragmentation pattern is largely common to all the accessible valence-ionized states of the chiller, consistent with rapid conversion to the ionic ground state before fragmentation. However, the highest-lying state of Li2Cl2+, (2)A(g). shows enhanced propensity for Li+ as dissociation product. (C) 2012 Elsevier B.V. All rights reserved.
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| 10. |
- Tchaplyguine, Maxim, et al.
(författare)
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Size-dependent evolution of electronic structure in neutral Pb clusters-As seen by synchrotron-based X-ray photoelectron spectroscopy
- 2014
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 195, s. 55-61
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Tidskriftsartikel (refereegranskat)abstract
- Neutral Pb clusters in the size range from a few tens of atoms up to similar to 100 atoms are studied using synchrotron-based photoelectron spectroscopy. The electronic structure is seen to differ increasingly from that of the solid when the cluster size decreases. The valence band narrows gradually - down to about one fifth of the solid-state band width at the smallest size of few tens of atoms. Simultaneously the Fermi-edge energy shifts further away from the solid value by more than 2 eV. The Pb 5d core level binding energy also increases and the spectral features broaden and change in shape. The changes observed for the valence and for the 5d response energies and shapes are discussed in the context of the metal-to-insulator transition observed earlier in Pb clusters below the critical size of 20-30 atoms/cluster. (C) 2014 Elsevier B.V. All rights reserved.
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