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| 2. |
- Carniato, S., et al.
(author)
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Photon-energy dependence of single-photon simultaneous core ionization and core excitation in CO2
- 2016
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In: PHYSICAL REVIEW A. - 2469-9926. ; 94:1
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Journal article (peer-reviewed)abstract
- We have studied the K-2V process corresponding to simultaneous K-shell ionization and K-shell excitation in the CO2 molecule. We define these K-2V states as super shake-up, at variance with the "conventional" K(-1)v(-1)V shake-up states. While the nature and evolution with photon energy of the conventional shake-up satellites has been the object of many studies, no such data on a large photon-energy range were previously reported on super shake-up. The CO2 molecule is a textbook example because it exhibits two well-isolated K-2V resonances (with V being 2 pi(u)* and 5 delta g*) with different symmetries resulting from shake-up processes of different origin populated in comparable proportions. The variation of the excitation cross section of these two resonances with photon energy is reported, using two different experimental approaches, which sheds light on the excitation mechanisms. Furthermore, double-core-hole spectroscopy is shown to be able to integrate and even expand information provided by conventional single-core-hole X-ray Photoelectron Spectroscopy (XPS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) techniques, revealing, for instance, g-g dipole forbidden transitions which are only excited in NEXAFS spectra through vibronic coupling.
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| 3. |
- Eland, J. H. D., et al.
(author)
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Spectra of the triply charged ion CS[sub 2][sup 3+] and selectivity in molecular Auger effects
- 2010
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 132:10, s. 104311-
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Journal article (peer-reviewed)abstract
- Spectra of triply charged carbon disulphide have been obtained by measuring, in coincidence, all three electrons ejected in its formation by photoionization. Measurements of the CS23+ ion in coincidence with the three electrons identify the energy range where stable trications are formed. A sharp peak in this energy range is identified as the 2Π ground state at 53.1±0.1 eV, which is the lowest electronic state according to ab initio molecular orbital calculations. Triple ionization by the double Auger effect is provisionally divided, on the basis of the pattern of energy sharing between the two Auger electrons into contributions from direct and cascade Auger processes. The spectra from the direct double Auger effect via S 2p, S 2s, and C 1s hole states contain several resolved features and show selectivity based on the initial charge localization and on the identity of the initial state. Triple ionization spectra from single Auger decay of S 2p -based core-valence states CS22+ show retention of the valence holes in this Auger process. Related ion-electron coincidence measurements give the triple ionization yields and the breakdown patterns in triple photoionization at selected photon energies from 90 eV to above the inner shell edges.
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| 4. |
- Feifel, Raimund, et al.
(author)
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Cationic double K-hole pre-edge states of CS2 and SF6
- 2017
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- Recent advances in X-ray instrumentation have made it possible to measure the spectra of an essentially unexplored class of electronic states associated with double inner-shell vacancies. Using the technique of single electron spectroscopy, spectra of states in CS2 and SF6 with a double hole in the K-shell and one electron exited to a normally unoccupied orbital have been obtained. The spectra are interpreted with the aid of a high-level theoretical model giving excellent agreement with the experiment. The results shed new light on the important distinction between direct and conjugate shake-up in a molecular context. In particular, systematic similarities and di erences between pre-edge states near single core holes investigated in X-ray absorption spectra and the corresponding states near double core holes studied here are brought out.
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| 5. |
- Goldsztejn, G., et al.
(author)
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Double-Core-Hole States in Neon: Lifetime, Post-Collision Interaction, and Spectral Assignment
- 2016
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:13
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Journal article (peer-reviewed)abstract
- Using synchrotron radiation and high-resolution electron spectroscopy, we have directly observed and identified specific photoelectrons from K-2V states in neon corresponding to simultaneous 1s ionization and 1s -> valence excitation. The natural lifetime broadening of the K-2V states and the relative intensities of different types of shakeup channels have been determined experimentally and compared to ab initio calculations. Moreover, the high-energy Auger spectrum resulting from the decay of Ne2+K-2 and Ne+K-2V states as well as from participator Auger decay from Ne+K-1L-1V states, has been measured and assigned in detail utilizing the characteristic differences in lifetime broadenings of these core hole states. Furthermore, post collision interaction broadening of Auger peaks is clearly observed only in the hypersatellite spectrum from K-2 states, due to the energy sharing between the two 1s photoelectrons which favors the emission of one slow and one fast electron.
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| 6. |
- Goldsztejn, G., 2017, et al.
(author)
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Experimental and theoretical study of the double-core-hole hypersatellite Auger spectrum of Ne
- 2017
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In: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 96
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Journal article (peer-reviewed)abstract
- We present the hypersatellite Auger spectrum of neon which contains the decay transitions of the K−2, K−2V, K−2L−1, K−2L−1V, and K−1L−1V states. The Auger decays of these types of core-hole states show different line shapes and linewidths which can be distinguished due to the high experimental resolution available for the present experiments. The individual Auger transitions are assigned based on various approaches. Complementary calculations are performed to assign the K−2L−1 → K−1L−3 and the K−2L−1V → K−1L−3V Auger transitions. Based on the obtained results we were able to derive the ratio for the double to single ionization yield.
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| 7. |
- Le Guen, K, et al.
(author)
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Influence of formation path on the CH2BrCl2+ dissociation dynamics
- 2005
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:8
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Journal article (peer-reviewed)abstract
- To get further insight into the CH2BrCl site-selective fragmentation previously observed upon inner-shell ionization, we have performed high-resolution Br 3d and Cl 2p Auger and spin-orbit resolved Br 3d Auger spectra, and studied the dissociation properties of the CH2BrCl2+ dication formed at threshold by means of threshold electron pair-ion coincidence measurements. The key point is that the origin of site-specific bond breaking is found in the Auger decay itself, as it preferentially populates selected dication states. Whereas the predominance of the C-Br bond breaking is observed in both threshold and inner-shell studies, no signature of selective C-Cl rupture is reported for the dication formed at threshold.
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| 8. |
- Žitnik, M., et al.
(author)
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Atomic two-color XUV interferometer
- 2023
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In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
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Conference paper (peer-reviewed)abstract
- We extend our recently published work which demonstrated the coherent control of population of 2s21S doubly excited state in helium by tuning the interference of ω1 + ω1 and ω3 − ω1 two-photon excitation paths [1]. The maximum yield of electrons from 2s2 autoionization was observed when the two-color phase difference matched phase difference of the atomic amplitudes describing the two alternative excitation paths. A displacement of position of the maximum yield in the same reference frame therefore signals the presence of an additional phase shifting agent along any of the two paths and also provides a measure of the corresponding phase shift. This constitutes the operational principle of an atomic XUV interferometer which is comparable to the well-known RABBITT method based on using a combination of XUV and IR light pulses [2]. The work was performed at LDM beamline at the free-electron-laser facility FERMI in Trieste (Italy). The phase difference of the two components of the light pulse was set by slightly delaying the ω3 emission from the last three undulators with respect to the ω1 emission produced by the first three undulators and this was achieved by delaying the generating electron bunch by properly adjusted magnetic chicane in between the two undulator sections.
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| 9. |
- Zitnik, M., et al.
(author)
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Interference of two-photon transitions induced by XUV light
- 2022
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In: Optica. - : Optica Publishing Group. - 2334-2536. ; 9:7, s. 692-700
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Journal article (peer-reviewed)abstract
- The relative phase of first (omega(1)) and third harmonics (omega(3)) extreme ultraviolet light pulses was varied to control the population of the 2s(2) state in helium through the interference of omega(1) + omega(1) and omega(3) - omega(1) two-photon excitation paths. The population was monitored by observing the total electron yield due to the 2s(2) autoionization decay. Maximum yield occurs when the relative phase of the two harmonics matches the phase difference of complex atomic amplitudes governing the two excitation paths. The calculated trend of atomic phase differences agrees well with the measured data in the spectral region of the resonance, provided that time-reversed -omega(1) + omega(3) path is also taken into account. These results open the way to accessing phase differences of two-photon ionization paths involving energetically distant intermediate states and to perform interferometry in the extreme ultraviolet range by monitoring final state populations. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
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| 10. |
- Brasse, Felix, et al.
(author)
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Time-resolved inner-shell photoelectron spectroscopy : From a bound molecule to an isolated atom
- 2018
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In: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 97:4
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Journal article (peer-reviewed)abstract
- Due to its element and site specificity, inner-shell photoelectron spectroscopy is a widely used technique to probe the chemical structure of matter. Here, we show that time-resolved inner-shell photoelectron spectroscopy can be employed to observe ultrafast chemical reactions and the electronic response to the nuclear motion with high sensitivity. The ultraviolet dissociation of iodomethane (CH3I) is investigated by ionization above the iodine 4d edge, using time-resolved inner-shell photoelectron and photoion spectroscopy. The dynamics observed in the photoelectron spectra appear earlier and are faster than those seen in the iodine fragments. The experimental results are interpreted using crystal-field and spin-orbit configuration interaction calculations, and demonstrate that time-resolved inner-shell photoelectron spectroscopy is a powerful tool to directly track ultrafast structural and electronic transformations in gas-phase molecules.
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