| 1. |
- Eland, J. H. D., et al.
(author)
-
Spectra of the triply charged ion CS23+ and selectivity in molecular Auger effects
- 2010
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 132:10, s. 104311-
-
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 (2)Pi 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.
|
|
| 2. |
- Jarraya, M., et al.
(author)
-
Doubly ionized OCS bond rearrangement upon fragmentation - experiment and theory
- 2023
-
In: Physical Chemistry Chemical Physics. - 1463-9076. ; 25:29, s. 19435-19445
-
Journal article (peer-reviewed)abstract
- The dissociation of OCS2+ ions formed by photoionization of the neutral molecule at 40.81 eV is examined using threefold and fourfold electron-ion coincidence spectroscopy combined with high level quantum chemical calculations on isomeric structures and their potential energy surfaces. The dominant dissociation channel of [OCS](2+) is charge separation forming CO+ + S+ ion pairs, found here to be formed with low intensity at a lower-energy onset and with a correspondingly smaller kinetic energy release than in the more intense higher energy channel previously reported. We explain the formation of CO+ + S+ ion pairs at low as well as higher ionization energies by the existence of two predissociation channels, one involving a newly identified COS2+ metastable state. We conclude that the dominant CO+ + S+ channel with 5.2 eV kinetic energy release is reached upon OCS2+ & RARR; COS2+ isomerization, whereas the smaller kinetic energy release (of & SIM;4 eV) results from the direct fragmentation of OCS2+ (X-3 & sigma;(-)) ions. Dissociation of the COS2+ isomer also explains the existence of the minor C+ + SO+ ion pair channel. We suggest that isomerization prior to dissociation may be a widespread mechanism in dications and more generally in multiply charged ion dissociations.
|
|
| 3. |
- Žitnik, M., et al.
(author)
-
Atomic two-color XUV interferometer
- 2023
-
In: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023. - 9798350345995
-
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.
|
|
| 4. |
- Céolin, D., et al.
(author)
-
Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution
- 2017
-
In: Physical Review Letters. - 0031-9007. ; 119:26
-
Journal article (peer-reviewed)abstract
- X-ray photoelectron and KLL Auger spectra were measured for the K+ and Cl- ions in aqueous KCl solution. While the XPS spectra of these ions have similar structures, both exhibiting only weak satellites near the main line, the Auger spectra differ dramatically. Contrary to the chloride case, a very strong extra peak was found in the Auger spectrum of K+ at the low kinetic energy side of the D1 state. Using the equivalent core model and ab initio calculations this spectral feature was assigned to electron transfer processes from solvent water molecules to the solvated cation. The observed charge transfer processes are suggested to play an important role in charge redistribution following single and multiple core-hole creation in atoms and molecules placed into environment.
|
|
| 5. |
- Eland, J. H. D., et al.
(author)
-
Spectra of the triply charged ion CS[sub 2][sup 3+] and selectivity in molecular Auger effects
- 2010
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 132:10, s. 104311-
-
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.
|
|
| 6. |
- Journel, Loïc, et al.
(author)
-
Resonant double Auger decay in carbon K-shell excitation of CO
- 2008
-
In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:4, s. 14-042710
-
Journal article (peer-reviewed)abstract
- We have studied double Auger decay after C 1s→2 photoexcitation in gas phase carbon monoxide. Two distinct processes, namely direct double Auger decay and cascade double Auger decay, are identified and studied in detail using multiple coincidence techniques. Cascade Auger decay is shown to be the overall dominant process. Decay channels involving the dissociation of the molecule followed by autoionization of the oxygen fragments are observed.
|
|
| 7. |
|
|
| 8. |
- Zitnik, M., et al.
(author)
-
Interference of two-photon transitions induced by XUV light
- 2022
-
In: Optica. - : Optica Publishing Group. - 2334-2536. ; 9:7, s. 692-700
-
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
|
|
| 9. |
- Carniato, S., et al.
(author)
-
Photon-energy dependence of single-photon simultaneous core ionization and core excitation in CO2
- 2016
-
In: PHYSICAL REVIEW A. - 2469-9926. ; 94:1
-
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.
|
|
| 10. |
- Céolin, Denis, et al.
(author)
-
A rotatable electron spectrometer for multicoincidence experiments
- 2010
-
In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 81:6
-
Journal article (peer-reviewed)abstract
- We have developed a rotatable hemispherical spectrometer with good energy and angular resolution, which can be positioned with the lens axis arbitrarily within a solid angle of 1 pi. The collection angle of the emitted electrons with respect to the polarization axis of the light is set by means of a three-axes goniometer, operating under vacuum. An important requirement for this setup was the possibility to perform coincidences between the electron analyzed by the spectrometer and one or several other particles, such as ions, electrons, or photons. The lens system and the hemispheres have been designed to accommodate such experimental demands, regarding parameters such as the resolving power, the acceptance angle, or the width of the kinetic energy window which can be recorded for a given pass energy. We have chosen to detect the impact position of the electron at the focal plane of the hemispherical analyzer with a delay line detector and a time-to-digital converter as acquisition card rather than using a conventional charge-coupled device camera. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3449333]
|
|
| 11. |
|
|
| 12. |
- Eland, John H. D., et al.
(author)
-
Triple ionization of CO(2) by valence and inner shell photoionization
- 2011
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 135:13, s. 134309-
-
Journal article (peer-reviewed)abstract
- Spectra of triply ionized CO(2) have been obtained from photoionization of the molecule using soft x-ray synchrotron light and an efficient multi-electron coincidence technique. Although all states of the CO(2)(+++) trication are unstable, the ionization energy for formation of molecular ions at a geometry similar to that of the neutral molecule is determined as 74 +/- 0.5 eV.
|
|
| 13. |
- Iwayama, H., et al.
(author)
-
A local chemical environment effect in site-specific Auger spectra of ethyl trifluoroacetate
- 2013
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 138:2, s. 024306-
-
Journal article (peer-reviewed)abstract
- We have investigated a local chemical environment effect on Auger spectra of ethyl trifluoroacetate (C4H5F3O2), using multi-electron coincidence spectroscopy and high-resolution electron spectroscopy. Site-specific KVV Auger spectra for each carbon atom, and for the fluorine and oxygen atoms are presented. The extent of hole localization in the final dicationic states was investigated with the help of theoretical calculations based on a two-hole population analysis. The Auger spectra have been simulated using a statistical approach. It is found that all Auger decays populate mainly localized dicationic states, with the two holes located either on the same fluorine atom or on adjacent fluorine atoms. While the decay of the F 1s hole populates exclusively the former states, the latter class of states is also populated by the decay of the C and O 1s holes.
|
|
| 14. |
- Mailhiot, M., et al.
(author)
-
Multielectron coincidence spectroscopy of the Ar2+(2p-2) double-core-hole decay
- 2023
-
In: Physical Review A. - 2469-9926. ; 107:6
-
Journal article (peer-reviewed)abstract
- The dominant decay pathways of argon 2p-2 double-core-hole states have been investigated using synchrotron radiation and a magnetic-bottle-type spectrometer coupled with an ion time-of-flight spectrometer. This experiment allows for efficient multi-electron-ion coincidence measurements, and thus for following the Auger cascade step by step in detail. Dominant decay pathways leading to Ar4+ final states via Ar3+ intermediate states have been assigned with the help of theoretical ab initio calculations. The weak correlated decay of the two core holes by emission of a single Auger electron, leading to Ar3+ final states, has been observed at 458.5-eV kinetic energy. Compared to the total decay of the 2p-2 double core vacancies, this two-electron-one-electron process was measured to have a branching ratio of 1.9 x 10-3 & PLUSMN; 1.0 x 10-3. Furthermore, the remaining decay paths of the Ar1+ (1s-1) core hole to higher charge states and their respective contributions to the total yield have been analyzed and show very good agreement with theoretical results.
|
|
| 15. |
- Mailhiot, M., et al.
(author)
-
Search for the interatomic Auger effect in Nitrous Oxide
- 2023
-
In: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 265
-
Journal article (peer-reviewed)abstract
- The interatomic Auger effect following O 1s ionization in N2O has been experimentally investigated using multi-electron coincidence spectroscopy. The expected transition energies have been established by comparison to the measured N 1s−1v−1 core-valence double ionization energies. We describe a procedure to eliminate the background of two competing processes contributing spectroscopic signatures to the same energy range, namely double Auger decay of the O 1s vacancy and direct single-photon double ionization into the N 1s−1v−1 states. While the interatomic Auger transitions could not be successfully isolated, we provide an upper boundary of the transition probability of 0.07% with respect to the dominant single Auger decay after O 1s ionization.
|
|
| 16. |
- Puettner, R., et al.
(author)
-
Hidden double excitations in the oxygen inner-shell ionization continuum of CO
- 2013
-
In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 15, s. 033003-
-
Journal article (peer-reviewed)abstract
- Auger decay spectra of CO subsequent to O 1s ionization with 549.85 eV photons, i.e. close to the top of the shape resonance, are presented. Their comparison with the normal Auger spectrum recorded at a photon energy well above the shape resonance reveals distinct features. In particular, in the energy region of the O 1s(-1) -> b(1)Pi and O 1s(-1) -> a(1)Sigma(+) Auger transitions which are well known to consist of vibrational progressions, additional narrow lines are revealed by the spectra recorded at 549.85 eV. In a detailed fit analysis of these Auger spectra it was possible to show that the newly found lines do not exhibit the expected distortions caused by post-collision interaction. This observation identifies these lines as caused by a different mechanism, such as resonant Auger decay processes of doubly excited states. The transitions are assigned using energy and intensity arguments in combination with complementary angular distribution measurements for the Auger electrons.
|
|
