| 1. |
- Andersson, E., et al.
(författare)
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Formation of Kr3+ via core-valence doubly ionized intermediate states
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032502-
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Tidskriftsartikel (refereegranskat)abstract
- The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon 3d(9)4p(5) core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the 4s(2)4p(3) and 4s(1)4p(4) configurations. The photon energy used was h nu = 150 eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr2+ are observed between 120 and 125 eV, whereas the final states of Kr3+ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.
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| 2. |
- Andersson, Egil, 1981-, et al.
(författare)
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Multielectron coincidence study of the double Auger decay of 3d-ionized krypton
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:4, s. 043418-
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Tidskriftsartikel (refereegranskat)abstract
- Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr+, and one involving single Auger transitions from Kr2+ created by direct single-photon double ionization. The decay of the 3d(9) D-2(5/2,3/2) states in Kr+ has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s(2)4p(3) S-4, D-2, and P-2 states of Kr3+ are analyzed and energies of seven intermediate states in Kr2+ are given. A preliminary investigation of the decay paths from Kr+ 3d (9)4p(5)nl shake-up states has also been carried out.
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| 3. |
- Andersson, Jonas, et al.
(författare)
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Triple ionization of atomic Cd involving 4p(-1) and 4s(-1) inner-shell holes
- 2015
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Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 92:2
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Tidskriftsartikel (refereegranskat)abstract
- The triple ionization spectrum of atomic Cd formed upon the removal of a 4p or a 4s inner-shell electron and subsequent Auger decays has been obtained at 200 eV photon energy. By using a versatile multielectron coincidence detection technique based on a magnetic bottle spectrometer in combination with multiconfiguration Dirac-Fock calculations, Auger cascades leading to tricationic final states have been analyzed and final-state configurations have been identified. The most prominent Auger cascades leading to the ground state of Cd3+ have been identified in good agreement with theory.
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| 4. |
- Ehara, M., et al.
(författare)
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Symmetry and vibrationally resolved absorption spectra near the N K edges of N2O : experiment and theory
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 83:6, s. 062506-
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Tidskriftsartikel (refereegranskat)abstract
- In this study, angle-resolved energetic-ion yield spectra were measured in the N 1s excitation region of N2O. A Franck-Condon analysis based on ab initio two-dimensional potential energy surfaces of the core-excited Rydberg states, which were calculated by the symmetry-adapted cluster-configuration interaction method, reproduced observed vibrational excitations specific to the individual Rydberg states well and enabled quantitative assignments. Geometric changes in the terminal nitrogen N-t 1s and the central nitrogen N-c 1s excited states with respect to the 3p pi, 3p sigma, and 4s sigma transitions were analyzed. The coupling of these valence and Rydbergs states was examined based on the second moment analysis. Irregular Rydberg-state behavior in the N-c 1s(-1) 4s sigma state was observed.
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| 5. |
- Kloda, Tomasz, et al.
(författare)
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Strong-field photoionization of O2 at intermediate light intensity
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:3, s. 033431-
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Tidskriftsartikel (refereegranskat)abstract
- We investigated by electron spectroscopy the strong-field multiphoton ionization of O-2 molecules with ultrashort laser pulses in the intensity range between the multiphoton and tunneling regimes. The ionization proceeds by at least three different mechanisms, in addition to the eight- and nine-photon nonresonant pathways. Transient multiphoton resonances with vibrational Rydberg levels give rise to direct Freeman-type peaks with sublaser linewidth and spin-orbit splitting. Some resonance levels actually become populated and yield extremely narrow lines because of postpulse vibrational autoionization. When the lowest photon order resonance channel for the Rydberg states is closed, a third contribution becomes dominant with a main peak at 0.4 eV that shares its main properties with the recently discovered universal low-energy structure in the electron spectra of atoms and molecules [C. I. Blaga et al., Nat. Phys. 5, 335 (2009); W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)]. The variation of the Freeman resonance spectrum with the laser peak intensity is well correlated with the vibronic Franck-Condon factors for the overlap of the intermediate Rydberg state with the O-2 ground state. Accordingly, the Freeman peaks could be unambiguously assigned to individual vibronic multiphoton resonances, and the disappearance of the Freeman resonances at a certain laser intensity could be explained. The population of the autoionizing Rydberg states could be assigned similarly to such vibronic resonances.
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| 6. |
- Linusson, Per, et al.
(författare)
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Complete double valence photoionization study of the electron spectra of krypton
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 88:2, s. 022510-
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Tidskriftsartikel (refereegranskat)abstract
- Double photoionization spectra of Kr have been recorded using monochromatized synchrotron radiation of 88 eV photon energy and a versatile multielectron coincidence time-of-flight spectroscopy technique. The formation of the Kr2+ states of the lowest-energy configuration 4s(2)4p(4) is partly direct, producing electron pairs with a continuous distribution, and partly indirect via superexcited singly ionized states. The superexcited Kr+ states show strong and hitherto unexplained selectivity in branching to final Kr2+ states. Kr2+ states based on excited configurations are formed mainly by direct double photoionization.
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| 7. |
- Linusson, Per, 1981-, et al.
(författare)
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Double ionization of atomic cadmium
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 83:2, s. 023424-
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Tidskriftsartikel (refereegranskat)abstract
- We have recorded the double photoionization spectrum of atomic Cd at four different photon energies in the range 40-200 eV. The main channel is single ionization and subsequent decay of excited Cd(+) states, some involving Coster-Kronig processes, whereas direct double ionization is found to be weak. The decay of the excited Cd(+) states shows a strong selectivity, related to the configuration of the final state. Double ionization leading to the Cd(2+) ground state is investigated in some detail and is found to proceed mainly through ionization and decay of 4d correlation satellites. The most prominent autoionization peaks have been identified with the aid of quantum-mechanical calculations.
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| 8. |
- Linusson, Per, 1981-, et al.
(författare)
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Single-photon multiple ionization forming double vacancies in the 2p subshell of argon
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 87:4, s. 043409-
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Tidskriftsartikel (refereegranskat)abstract
- Single-photon ionization leading to two vacancies in the 2p subshell of argon is investigated experimentally using the photoelectron time-of-flight magnetic bottle coincidence technique. Three peaks corresponding to the 3P, 1D, and 1S states of the dication are found in the ionization energy range 535 to 562 eV. Multiconfigurational Dirac-Fock calculations were performed to estimate the single-photon double-ionization cross sections. Reasonable agreement between the measured and simulated spectra is found if single and double excitations are taken into account in the wave-function expansion.
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| 9. |
- Linusson, Per, 1981-, et al.
(författare)
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Structure sensitivity of double inner-shell holes in sulfur-containing molecules
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 83:2, s. 022506-
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Tidskriftsartikel (refereegranskat)abstract
- To demonstrate the structure sensitivity of double inner-shell hole spectroscopy, we have measured energies of H(2)S(2+), SO(2)(2+), and CS(2)(2+) with the two vacancies in the sulfur 2p shell using a multielectron coincidence technique combined with synchrotron radiation. We describe how to extract intrinsic chemical information which is masked by the orbital relaxation effect in conventional core-level photoelectron spectroscopy.
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| 10. |
- 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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