| 1. |
- Feifel, Raimund, et al.
(författare)
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Probing the valence character of O-1s -> Rydberg excited O-2 by participator Auger decay measurements and partial ion yield spectroscopy following x-ray absorption
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 126:17, s. 174304-
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Tidskriftsartikel (refereegranskat)abstract
- The valence character of O 1s -> Rydberg excited O-2 is investigated by means of participator Auger decay spectroscopy, performed at selected photon energies across the K-shell resonance region, and by means of partial ion yield x-ray absorption spectroscopy. For several of the excitation energies studied, the authors find substantial sigma(*)((4)Sigma(-)(u),(2)Sigma(-)(u)) valence character being mixed with ns sigma and np sigma ((4)Sigma(-)(u),(2)Sigma(-)(u)) Rydberg states. An experimental indication of a coupling between the channels associated with quartet and doublet ion cores is considered and discussed. New spectroscopic constants are derived for the singly ionized X (2)Pi(g) state of O-2 based on the observation of at least 20 vibrational sublevels.
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| 2. |
- Gel'mukhanov, Faris, et al.
(författare)
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Young's double-slit experiment using two-center core-level photoemission : Photoelectron recoil effects
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 156, s. 265-269
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Tidskriftsartikel (refereegranskat)abstract
- Core-level photoemission from N-2 can be considered an analogue of Young's double-slit experiment (YDSE) in which the double-slit is replaced by a pair of N 1s orbitals. The measured ratio between the 1 sigma(g) and 1 sigma(u) photoionization cross-sections oscillates as a function of photoelectron momentum, due to two-center YDSE interference, exhibiting a remarkable dependence on the vibrational sub-levels of the core ionized state. We theoretically demonstrate that the recoil of the photoelectron given to the ionized N atom strongly influences this interference pattern. The reason for this is that the momentum transfer affects the phases of the photoionization amplitudes.
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| 3. |
- Kukk, E., et al.
(författare)
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Electronic state dependence in the dissociation of core-ionized methane
- 2007
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 40:18, s. 3677-3692
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Tidskriftsartikel (refereegranskat)abstract
- Methane and deuteromethane molecules were core ionized using synchrotron radiation, and the ionic fragments from the molecular dissociation were detected in coincidence with the Auger electrons. The electron - ion coincidence spectra are analysed in terms of partial ion yields and ion kinetic energy distributions, both as functions of electron kinetic energy. The dependence of the fragmentation patterns on the electronic character of the Auger final states as well as on the excess energy available for dissociating the molecule is studied. The analysis reveals marked differences in the dissociation of the 2a(1)(-2) and 2a(1)(-1) 1t(2)(-1) states, interpreted as an `excess- energy- dependent' concerted dissociation process for the 2a(1)(-2) state and an ` electronic- state- dependent' sequential process for the 2a(1)(-1) 1t(2)(-1) state.
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| 4. |
- Liu, X. J., et al.
(författare)
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Young's double-slit experiment using two-center core-level photoemission : Photoelectron scattering effects
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 156, s. 73-77
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Tidskriftsartikel (refereegranskat)abstract
- Core-level photoemission from N-2 can be considered as an analogue of Young's double-slit experiment (YDSE) in which the double-slit is replaced by a pair of N 1s orbitals. N 1s photoelectron spectra of N-2 are measured in the extended photon energy region up to similar to 1 keV at unprecedented resolution. The measured ratio between the 1 sigma(g) and 1 sigma(u) photoionization cross-sections oscillates as a function of electron momentum due to interference effects analogue to YDSE. We found a shift of the interference pattern with respect to a prediction by a simple model for coherent two-center emission, the Cohen-Fano formula, and attributed it to photoelectron scattering by the neighboring atom. We demonstrate that the shift can be used to determine the scattering phase of the photoelectron.
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| 5. |
- Piancastelli, Maria Novella, et al.
(författare)
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Electronic Structure of Core-excited and Core-ionized Methyl Oxirane
- 2007
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 156, s. 259-264
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Tidskriftsartikel (refereegranskat)abstract
- We report a detailed analysis of the electronic structure of methyl oxirane, including core-level photoelectron spectroscopy, X-ray absorption at both C and O K-shells, resonant Auger and normal Auger spectroscopy. The X-ray absorption spectra (XAS) around the C K-edge can be easily interpreted on the ground of the chemical shift between the carbon atoms with different chemical environments. The X-ray absorption data around the O K-edge are quite structureless, hinting for a likely fragmentation process (possibly implying a ring-opening reaction). In resonant Auger spectra obtained after excitation below both the C 1s and O 1s ionization thresholds we notice a predominance of spectator decay implying a strong mixing between empty molecular orbitals and Rydberg states.
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