| 1. |
- Aksela, S., et al.
(författare)
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Accurate free atom-solid binding energy shifts for Au and Ag
- 2012
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 185:8-9, s. 273-277
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Tidskriftsartikel (refereegranskat)abstract
- Binding energy shifts between atomic and solid states have been observed with improved accuracy for All 4f and Ag 3d core levels applying a simultaneous measurement method. Also the 3d photoelectron spectrum and binding energies of free Ag atoms have been observed for the first time. New values determined as free atom to bulk solid shifts deviate considerably from previous estimate for Au but agree reasonably well for Ag. The valence bands were also found to shift rather accurately by the same amount as the core levels. (C) 2012 Published by Elsevier B.V.
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| 2. |
- Holappa, M., et al.
(författare)
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Atom-solid binding energy shifts for K 2p and Rb 3d sublevels
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 184:7, s. 371-374
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Tidskriftsartikel (refereegranskat)abstract
- Binding energy shifts between free and solid state atoms for K 2p and Rb 3d photolines have been determined by measuring the vapor and solid state spectra simultaneously in similar experimental conditions applying synchrotron radiation excited photoelectron spectroscopy. This method has the important benefit that the work function is not needed to correct for different reference energy levels, therefore much more accurate values for binding energy shifts are obtained. (C) 2011 Elsevier B.V. All rights reserved.
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| 3. |
- Niskanen, Johannes, et al.
(författare)
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Experimental and theoretical study of core-valence double photoionization of OCS
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:4, s. 043436-
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Tidskriftsartikel (refereegranskat)abstract
- O 1s, C 1s, and S 2p core-valence double ionization electron spectra of the OCS molecule have been obtained experimentally by a time-of-flight photoelectron-photoelectron coincidence spectroscopy technique. In order to analyze and assign the spectral features observed, we present a protocol for computing core-valence ionization energies of such systems. The protocol is based on a restricted active space multiconfigurational self-consistent field (MCSCF) methodology with a freeze-relax procedure to guarantee a correct core-valence state root index without variational collapse. Corrections for extended dynamical correlation and core-core correlation, respectively, are made by multiconfigurational perturbation theory and by uncontracted basis set Moller-Plesset theory. Envisioning applications to larger molecules, a spin-restricted open-shell density functional method is also applied for the lowest core-valence energies. Furthermore, cross sections through a scheme for computing multiatom Auger transitions generating core-valence holes are presented. We find that the procedure outlined is capable of deriving the energy onset of core-valence ionization within a fraction of an eV and that assignments can be made of the most salient spectral features.
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| 4. |
- Niskanen, Johannes, et al.
(författare)
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Photoelectron angular distribution and linear magnetic dichroism in the 4p photoemission from Rb atoms
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:1, s. 013406-
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Tidskriftsartikel (refereegranskat)abstract
- The angular distribution of photoelectrons and linear magnetic dichroism in the angular distribution for the 4p photoemission from Rb atoms in the ground state, oriented by laser pumping, were measured in the photon energy range from 50 to 100 eV. The experimental results are compared with the multiconfiguration Dirac-Fock (MCDF) calculations. We show that the zero-crossing of the dichroism as a function of energy is connected with the Cooper minimum in the cross section. This fact can be used for an accurate determination of the position of the Cooper minimum.
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| 5. |
- Niskanen, Johannes, et al.
(författare)
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Valence photoionization of the LiCl monomer and dimer
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:4, s. 043401-
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports a study of valence photoionization of the LiCl monomer and dimer. The behavior of the photoionization partial cross section for molecular valence orbitals was measured as a function of photon energy between 15 and 35 eV. A square-integrable-function method was used to model the ionization partial cross section in both the LiCl monomer and dimer.
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| 6. |
- Partanen, L., et al.
(författare)
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2s photoionization and subsequent Auger cascade in atomic Si
- 2010
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:6
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Tidskriftsartikel (refereegranskat)abstract
- The 2s photoionization and subsequent Auger transition cascade in atomic Si were studied by means of synchrotron-radiation-induced electron spectroscopy. After the 2s photoionization, the core hole states decay predominantly by a two-step Auger transition cascade into the triply ionized [Ne]nl states. The ionization channels of the 2s core-ionized Si+ atoms to Si3+ ions were observed by measuring the conventional Auger electron spectra of the L-1-L2,3M Coster-Kronig transitions and the L2,3M-MMM Auger transitions. The observed L-1-L2,3M and L2,3M-MMM Auger spectra were analyzed by means of extensive multiconfiguration Dirac-Fock computations. We found that the electron correlation plays a prominent role in the Auger cascade, especially for the final-step Auger L2,3M-MMM spectrum. Additionally, it was seen that the L2,3M-MMM Auger spectrum of Si includes more Auger groups than the isoelectronic L-2,L-3-MMAuger spectrum of Al. Thus, more information on the intermediate ionic states is obtained if they are produced by Auger cascade rather than by direct photoionization.
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| 7. |
- Patanen, M., et al.
(författare)
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4f photoionization and subsequent Auger decay in atomic Pb: Relativistic effects
- 2011
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 83:5
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution 4f photoelectron and subsequent Auger-electron spectra have been measured from free Pb atoms using synchrotron radiation. The fine structure of the spectra has been investigated theoretically by calculating the energies and intensities for 4f photoionization and Auger decay processes using the multiconfigurational Dirac-Fock approach. The role of the relativistic effects in the ground and singly and doubly ionized states has been studied on the basis of computed results and their comparison with experiment.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Thiagarajan, Balasubramanian, et al.
(författare)
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The Normal Incidence Monochromator Beamline I3 on MAX III
- 2010
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 1234, s. 661-664
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Konferensbidrag (refereegranskat)abstract
- On the 700 MeV MAX III ring at MAX-lab, a 6.65 m off-axis eagle type monochromator beamline has recently been commissioned. The beamline is sourced by an apple type variable polarization undulator. The energy range of the beamline is 4.6-50 eV and the resolving power achieved is more than 100,000. There are two branch lines, one for angle and spin resolved photoemission studies from solids and the other for gas phase and luminescence experiments. We present the design and performance of the beamline.
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