| 1. |
- Andersson, T., et al.
(författare)
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Electronic structure transformation in small bare Au clusters as seen by x-ray photoelectron spectroscopy
- 2017
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:1
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Tidskriftsartikel (refereegranskat)abstract
- Free bare gold clusters in the size range from few tens to few hundred atoms (<= 1 nm dimensions) have been produced in a beam, and the size-dependent development of their full valence band including the 5d and 6s parts has been mapped 'on the fly' by synchrotron-based photoelectron spectroscopy. The Au 4f core level has been also probed, and the cluster-specific Au 4f ionization energies have been used to estimate the cluster size. The recorded in the present work valence spectra of the small clusters are compared with the spectra of the large clusters (N similar to 10(3)) created by us using a magnetron-based gas aggregation source. The comparison shows a substantially narrower 5d valence band and the decrease in its splitting for gold clusters in the size range of few hundred atoms and below. Our DFT calculations involving the pseudopotential method show that the 5d band width of the ground state increases with the cluster size and by the size N = 20 becomes comparable with the experimental width of the valence photoelectron spectrum. Similar to the earlier observations on supported clusters we interpret our experimental and theoretical results as due to the undercoordination of a large fraction of atoms in the clusters with N similar to 10(2) and below. The consequences of such electronic structure of small gold clusters are discussed in connection with their specific physical and chemical properties related to nanoplasmonics and nanocatalysis.
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| 2. |
- 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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| 3. |
- G. Öhrwall, M. Tchaplyguine, M. Gisselbrecht, M. Lundwall, R. Feifel, T. Rander, J. Schulz, R. R. T. Marinho, A. Lindgren, S. L. Sorensen, S. Svensson and O. Björneholm
(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: J. Phys. B: At. Mol. Opt. Phys. ; :36, s. 3937-
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Hautala, Lauri, et al.
(författare)
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Experimental observation of structural phase transition in CsBr clusters
- 2017
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Ingår i: Physical Review B. - 1098-0121. ; 95:4
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Tidskriftsartikel (refereegranskat)abstract
- Formation and growth of CsBr clusters embedded in unsupported Ar clusters was studied using synchrotron radiation photoelectron spectroscopy. The development of the core-level electronic structure for cluster sizes between a few and a few hundred atoms contained information about the local coordination of the constituent particles. The experimental results indicate that a gradual structural phase transition from NaCl structure to CsCl structure for CsBr clusters takes place at around 160 atoms per cluster.
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| 5. |
- Mikkelä, M.-H., et al.
(författare)
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Bismuth-oxide nanoparticles : study in a beam and as deposited
- 2024
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 26:13, s. 10369-10381
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Tidskriftsartikel (refereegranskat)abstract
- Bi2O3 is a promising material for solid-oxide fuel cells (SOFC) due to the high ionic conductivity of some phases. The largest value is reached for its δ-phase, but it is normally stable at temperatures too high for SOFC operation, while nanostructured oxide is believed to have more suitable stabilization temperature. However, to manufacture such a material with a controlled chemical composition is a challenging task. In this work, we investigated the fabrication of nanostructured Bi2O3 films formed by deposition of free Bi-oxide nanoparticles created in situ. The particle-production method was based on reactive sputtering and vapour aggregation. Depending on the fabrication conditions, the nanoparticles contained either a combination of Bi–metal and Bi-oxide, or only Bi-oxide. Prior to deposition, the free particles were probed in the beam – by synchrotron-based photoelectron spectroscopy (PES), which allowed assessing their composition "on the-fly". The nanoparticle films obtained after deposition were studied by PES, scanning electron microscopy, transmission electron microscopy, and electron diffraction. The films' chemical composition, grain dimensions, and crystal structure were probed. Our analysis suggests that our method produced Bi-oxide films in more than one polymorph of Bi2O3.
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| 6. |
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| 7. |
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| 8. |
- Feifel, R, et al.
(författare)
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A quantitative analysis of the N 1s ->pi* photoabsorption profile in N-2: new spectroscopical constants for the core-excited state
- 2004
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 383:3-4, s. 222-229
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Tidskriftsartikel (refereegranskat)abstract
- The N 1s --> pi* photoabsorption profile of N-2 is quantitatively analysed. New spectroscopical constants for the N 1s(-1) pi* core-excited state are determined from NEXAFS spectra and compared to previously published data. The accuracy of the new spectroscopical constants is discussed and error bars are given for the present data analysis. The goodness of the new spectroscopical constants is demonstrated by lifetime vibrational interference (LVI) simulations of the resonant Auger decay from the N 1s(-1) pi* core-excited state to the A(2)Pi(u) singly ionized final state of N-2. These new values give a much better agreement with recently obtained experimental data compared to the previously published ones.
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| 9. |
- Foehlisch, A., et al.
(författare)
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Charge transfer dynamics in molecular solids and adsorbates driven by local and non-local excitations
- 2012
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 606:11-12, s. 881-885
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Tidskriftsartikel (refereegranskat)abstract
- Charge transfer pathways and charge transfer times in molecular films and in adsorbate layers depend both on the details of the electronic structure as well as on the degree of the initial localization of the propagating excited electronic state. For C6F6 molecular adsorbate films on the Cu(111) surface we determined the interplay between excited state localization and charge transfer pathways. In particular we selectively prepared a free-particle-like LUMO band excitation and compared it to a molecularly localized core-excited C1s -> pi* C6F6 LUMO state using time-resolved two-photon photoemission (tr-2PPE) and core-sole-clock (CHC) spectroscopy, respectively. For the molecularly localized core-excited C1s -> pi* C6F6 LUMO state, we separate the intramolecular dynamics from the charge transfer dynamics to the metal substrate by taking the intramolecular dynamics of the free C6F6 molecule into account Our analysis yields a generally applicable description of charge transfer within molecular adsorbates and to the substrate. (C) 2011 Published by Elsevier B.V.
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| 10. |
- 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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