| 1. |
- Travnikova, O., et al.
(författare)
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Ultrafast dissociation of ammonia : Auger Doppler effect and redistribution of the internal energy
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:10, s. 5842-5854
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Tidskriftsartikel (refereegranskat)abstract
- We study vibrationally-resolved resonant Auger (RAS) spectra of ammonia recorded in coincidence with the NH2+ fragment, which is produced in the course of dissociation either in the core-excited 1s−14a11 intermediate state or the first spectator 3a−24a11 final state. Correlation of the NH2+ ion flight times with electron kinetic energies allows directly observing the Auger-Doppler dispersion for each vibrational state of the fragment. The median distribution of the kinetic energy release EKER, derived from the coincidence data, shows three distinct branches as a function of Auger electron kinetic energy Ee: Ee + 1.75EKER = const for the molecular band; EKER = const for the fragment band; and Ee + EKER = const for the region preceding the fragment band. The deviation of the molecular band dispersion from Ee + EKER = const is attributed to the redistribution of the available energy to the dissociation energy and excitation of the internal degrees of freedom in the molecular fragment. We found that for each vibrational line the dispersive behavior of EKERvs. Ee is very sensitive to the instrumental uncertainty in the determination of EKER causing the competition between the Raman (EKER + Ee = const) and Auger (Ee = const) dispersions: increase in the broadening of the finite kinetic energy release resolution leads to a change of the dispersion from the Raman to the Auger one.
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| 2. |
- Boudjemia, N., et al.
(författare)
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Electron spectroscopy and dynamics of HBr around the Br 1s(-1) threshold
- 2020
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:46, s. 26806-26818
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive electron spectroscopic study combined with partial electron yield measurements around the Br 1s ionization threshold of HBr at approximately equal to 13.482 keV is reported. In detail, the Br 1s(-1) X-ray absorption spectrum, the 1s(-1) photoelectron spectrum as well as the normal and resonant KLL Auger spectra are presented. Moreover, the L-shell Auger spectra measured with photon energies below and above the Br 1s(-1) ionization energy as well as on top of the Br 1s(-1)sigma* resonance are shown. The latter two Auger spectra represent the second step of the decay cascade subsequent to producing a Br 1s(-1) core hole. The measurements provide information on the electron and nuclear dynamics of deep core-excited states of HBr on the femtosecond timescale. From the different spectra the lifetime broadening of the Br 1s(-1) single core-hole state as well as of the Br(2s(-2),2s(-1)2p(-1),2p(-2)) double core-hole states are extracted and discussed. The slope of the strongly dissociative HBr 2p(-2)sigma* potential energy curve is found to be about -13.60 eV angstrom(-1). The interpretation of the experimental data, and in particular the assignment of the spectral features in the KLL and L-shell Auger spectra, is supported by relativistic calculations for HBr molecule and atomic Br.
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| 3. |
- Feifel, Raimund, et al.
(författare)
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Cationic double K-hole pre-edge states of CS2 and SF6
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Goldsztejn, G., et al.
(författare)
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Double-Core-Hole States in Neon: Lifetime, Post-Collision Interaction, and Spectral Assignment
- 2016
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:13
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Goldsztejn, G., 2017, et al.
(författare)
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Experimental and theoretical study of the double-core-hole hypersatellite Auger spectrum of Ne
- 2017
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Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 96
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Koulentianos, Dimitris, 1987, et al.
(författare)
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Double-core-hole states in CH3CN: Pre-edge structures and chemical-shift contributions
- 2018
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149
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Tidskriftsartikel (refereegranskat)abstract
- Spectra reflecting the formation of single-site double-core-hole pre-edge states involving the N 1s and C 1s core levels of acetonitrile have been recorded by means of high-resolution single-channel photoelectron spectroscopy using hard X-ray excitation. The data are interpreted with the aid of ab initio quantum chemical calculations, which take into account the direct or conjugate nature of this type of electronic states. Furthermore, the photoelectron spectra of N 1s and C 1s singly core-ionized states have been measured. From these spectra, the chemical shift between the two C 1s(-1) states is estimated. Finally, by utilizing C 1s single and double core-ionization potentials, initial and final state effects for the two inequivalent carbon atoms have been investigated. Published by AIP Publishing.
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| 7. |
- Koulentianos, Dimitris, 1987, et al.
(författare)
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The O K-2V spectrum of CO: the influence of the second core-hole
- 2021
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18, s. 10780-90
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Tidskriftsartikel (refereegranskat)abstract
- Using synchrotron radiation in the tender X-ray regime, a photoelectron spectrum showing the formation of single site double-core-hole pre-edge states, involving the K shell of the O atom in CO, has been recorded by means of high-resolution electron spectroscopy. The experimentally observed structures have been simulated, interpreted and assigned, employing state-of-the-art ab initio quantum chemical calculations, on the basis of a theoretical model, accounting for their so-called direct or conjugate character. Features appearing above the double ionization threshold have been reproduced by taking into account the strong mixing between multi-excited and continuum states. The shift of the sigma* resonance below the double ionization threshold, in combination with the non-negligible contributions of multi-excited configurations in the final states reached, gives rise to a series of avoided crossings between the different potential energy curves.
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| 8. |
- Kukk, E., et al.
(författare)
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Energy Transfer into Molecular Vibrations and Rotations by Recoil in Inner-Shell Photoemission
- 2018
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:7
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Tidskriftsartikel (refereegranskat)abstract
- A mixture of CF4 and CO gases is used to study photoelectron recoil effects extending into the tender xray region. In CF4, the vibrational envelope of the C 1s photoelectron spectrum becomes fully dominated by the recoil-induced excitations, revealing vibrational modes hidden from Franck-Condon excitations. In CO, using CF4 as an accurate energy calibrant, we determine the partitioning of the recoil-induced internal excitation energy between rotational and vibrational excitation. The observed rotational recoil energy is 2.88(28) times larger than the observed vibrational recoil energy, well in excess of the ratio of 2 predicted by the basic recoil model. The experiment is, however, in good agreement with the value of 2.68 if energy transfer via Coriolis coupling is included.
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| 9. |
- Kukk, E., et al.
(författare)
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Unified treatment of recoil and Doppler broadening in molecular high-energy photoemission
- 2021
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Ingår i: New Journal of Physics. - : Institute of Physics Publishing (IOPP). - 1367-2630. ; 23:6
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Tidskriftsartikel (refereegranskat)abstract
- Doppler and recoil effects are an integral part of the photoemission process at the high kinetic energies reached in hard x-ray photo-electron spectroscopy (HAXPES) and have a major effect on the observed lineshape, resulting in broadening, energy losses and discrete excitations. These effects can be modeled with a high degree of detail for small systems like diatomic molecules, for larger systems such treatment is often superfluous as the fine spectral features are not observable. We present a united description of the Doppler and recoil effects for arbitrary polyatomic systems and offer an approximate description of the recoil- and Doppler-modified photoemission spectral lineshape as a practical tool in the analysis of HAXPES spectra of core-level photoemission. The approach is tested on the examples of carbon dioxide and pentane molecules. The C and O 1s photoelectron spectra of CO2 in gas phase were also measured at 2.3 and 7.0 keV photon energy at Synchrotron SOLEIL and the spectra were analyzed using the model description. The limitations and applicability of the approach to adsorbates, interfaces and solids is briefly discussed.
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| 10. |
- Li, S., et al.
(författare)
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Manifestation of postcollision interaction in Krypton LMN Auger spectra following K-shell photoionization
- 2022
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 106:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on an experimental and theoretical study of postcollision interaction (PCI) effects on L-2 - M4,5N2,3 Auger electrons measured above the Kr K-edge in which L-2 vacancies are primarily generated by KL2 x-ray emission. Such cascade processes, in which a deep inner-shell vacancy decays first by x-ray emission followed by Auger electron emission, is a strong decay mode in heavy atoms. The L-2 - M4,5N2,3 Auger electron peak is observed to become increasingly asymmetric with a shifting peak maximum as the absorbed x-ray energy approaches the K-shell ionization threshold. This is attributed to PCI energy exchanges of the Auger electron with the 1s photoelectron. To model the PCI effects, we have applied a semiclassical approach modified to account for the combined lifetimes of the K and L-2 hole states. In addition, our analysis treats several closely spaced Auger transitions with final ionic states having different terms and angular momenta.
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| 11. |
- Marchenko, T., et al.
(författare)
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Single and multiple excitations in double-core-hole states of free water molecules
- 2020
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 53:22
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined experimental and theoretical study of the double-core-hole photoelectron spectrum obtained in isolated water molecules irradiated with hard x-rays above the oxygen K -2 threshold. States of the type O K -2V and multiply excited states are created by single-photon absorption and subsequent one-electron emission. A detailed analysis enabled by high experimental resolution reveals dissociative nuclear dynamics in the K-2V pre-edge states. At the binding energies above the K- 2 double-ionization potential, a complex spectral pattern is observed and attributed to highly excited states involving multiple shake-up excitation processes with the aid of state- of-the-art theoretical calculations. A strong broadening due to the nuclear motion indicates a highly dissociative nature of these multiply excited states, in agreement with the theoretical analysis.
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| 12. |
- Marchenko, T., et al.
(författare)
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Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy
- 2018
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Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 98:6
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Tidskriftsartikel (refereegranskat)abstract
- We present a combined experimental and theoretical study of the Auger-emission spectrum following double core ionization and excitation of gas-phase water molecules with hard-x-ray synchrotron radiation above the O K-2 threshold. We observe an indication of ultrafast proton motion occurring within the 1.5 fs lifetime of the double-core-hole (DCH) states in water. Furthermore, we have identified symmetric and antisymmetric dissociation modes characteristic for particular DCH states. Our results serve as a fundamental reference for state-of-the-art studies of DCH dynamic processes in liquid water both at synchrotron and free-electron-laser facilities.
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| 13. |
- Martins, J. B., et al.
(författare)
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Electron delocalisation in conjugated sulfur heterocycles probed by resonant Auger spectroscopy
- 2022
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:14, s. 8477-8487
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Tidskriftsartikel (refereegranskat)abstract
- We propose a novel approach for an indirect probing of conjugation and hyperconjugation in core-excited molecules using resonant Auger spectroscopy. Our work demonstrates that the changes in the electronic structure of thiophene (C4H4S) and thiazole (C3H3NS), occurring in the process of resonant sulfur K-shell excitation and Auger decay, affect the stabilisation energy resulting from pi-conjugation and hyperconjugation. The variations in the stabilisation energy manifest themselves in the resonant S KL2,3L2,3 Auger spectra of thiophene and thiazole. The comparison of the results obtained for the conjugated molecules and for thiolane (C4H8S), the saturated analogue of thiophene, has been performed. The experimental observations are interpreted using high-level quantum-mechanical calculations and the natural bond orbital analysis.
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| 14. |
- Puttner, R., et al.
(författare)
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Argon 1s(-2) Auger hypersatellites
- 2020
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:2
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Tidskriftsartikel (refereegranskat)abstract
- The 1s(-2) Auger hypersatellite spectrum of argon is studied experimentally and theoretically. In total, three transitions to the final states 1s(-1)2p(-2)(S-2(e),D-2(e)) and 1s(-1)2s(-1)(S-1)2p(-1)(P-2(o)) are experimentally observed. The lifetime broadening of the 1s(-2) -> 1s(-1)2p(-2)(S-2(e),D-2(e)) states is determined to be 2.1(4) eV. For the used photon energy of h nu = 7500 eV a KK/K ionisation ratio of 2.5(3) x 10(-4) is derived. Generally, a good agreement between the experimental and present theoretical energy positions, linewidths, and intensities is obtained.
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| 15. |
- Püttner, R., et al.
(författare)
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Argon KLL Auger spectrum: Initial states, core-hole lifetimes, shake, and knock-down processes
- 2020
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Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 102:5
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art argon KLL Auger spectra measured using photon energies of hν=3216 and 3400 eV are presented along with an Ar [1s] photoelectron spectrum (square brackets indicate holes in the respective orbital). The two different photon energies used for measuring the Auger spectra allow distinguishing between the shake transitions during the Auger decay and the Auger transitions of the photoelectron satellites. A complete assignment of satellite transitions is provided, partially based on configuration-interaction calculations. In addition, Ar [1s3(s,p)]n′l′→[2p2(1D2)] transitions are observed, which can be explained by knock-down transitions leading to a direct exchange of angular momentum between the excited electron and the Auger electron. The lifetime broadenings of the Ar [2s] single-core-hole state and the [2s2] and [2s2p] double-core-hole states are also determined, confirming previously observed trends for double-core-hole states. © 2020 American Physical Society.
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| 16. |
- Püttner, R., et al.
(författare)
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Nonstatistical behavior of the photoionization of spin-orbit doublets
- 2021
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:8
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Tidskriftsartikel (refereegranskat)abstract
- The photoionization branching ratios of spin-orbit doublets are studied both experimentally and theoretically at energies several keV above threshold. The results show significant relativistic effects for Ar 2p in the autoionizing region below the 1s threshold, and large many-body effects for Xe 3d and 4d in the vicinity of the L-shell thresholds. The branching ratios in Xe are also found to vary significantly over very broad multi-keV energy regions both above and below the inner-shell thresholds. In addition, the Ar 2p study confirms experimentally the decades-old theoretical prediction that the nonresonant branching ratio does not approach the statistical (nonrelativistic) value, and, in fact, progressively diverges from statistical with increasing photon energy. © 2021 The Author(s). Published by IOP Publishing Ltd.
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| 17. |
- Boudjemia, N., et al.
(författare)
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Deep-core photoionization of krypton atoms below and above the 1s ionization threshold
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 101:5
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Tidskriftsartikel (refereegranskat)abstract
- Electronic relaxation of atomic Kr below and above the 1s ionization threshold is investigated experimentally using hard x-ray photoelectron spectroscopy. The experimental results are interpreted with the aid of relativistic Dirac-Fock calculations. The 1s orbital core-hole lifetime is extracted and the satellite's structures accompanying the photoelectron main line are assigned. Auger spectra recorded below and above the K edge are also investigated. In particular, the Auger cascade originating from vacancies of different origin in the L shell is analyzed in great detail. Competition between radiative KL versus nonradiative KLL Auger emission is emphasized.
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| 18. |
- Boudjemia, N., et al.
(författare)
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Experimental and theoretical study of the Kr L-shell Auger decay
- 2021
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 104:1
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Tidskriftsartikel (refereegranskat)abstract
- The LMM Auger spectra of krypton are measured using the photon energies hv = 1709 eV, 1792 eV, 1950 eV, and 13 keV. This approach allows separating the contributions from the various core holes L-1 , L-2., and L-3. Previously unobserved transitions are presented. Complementary theoretical work is performed allowing the assignment of the spectral features. The L2,3Y -MMY (Y = M-4,M-5, N-1,N-2,N-3) Auger transitions of Kr2+ formed via Coster-Kronig Auger decay of the core holes L-1 and L-2. are also investigated. These spectra comprise about 4000 and 13 000 transitions, respectively, so that only general statements on the assignment, such as the configurations involved in the transitions, can be given.
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| 19. |
- Ceballos, G, et al.
(författare)
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High-resolution X-ray absorption spectra of the pi* resonance of N-2 directly physisorbed on Cu(100)
- 2001
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Ingår i: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT. - : ELSEVIER SCIENCE BV. - 0168-9002. ; 467, s. 1560-1563
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution NEXAFS spectra of the pi* resonance of N-2 molecules directly physisorbed on a Cu(100) surface are reported. The vibrational fine structure of this resonance, even for very low coverages, could be resolved, allowing the performance of a vi
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| 20. |
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| 21. |
- Kolczewski, C., et al.
(författare)
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Detailed study of pyridine at the C1s and N1s ionization thresholds : The influence of the vibrational fine structure
- 2001
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 115:14, s. 6426-6437
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Tidskriftsartikel (refereegranskat)abstract
- High resolution, vibrationally resolved, near-edge x-ray absorption fine structure (NEXAFS) spectra at the C 1s and N 1s ionization thresholds of pyridine and deuterated d(5)-pyridine in the gas phase have been recorded. The high resolution of 65 meV (150 meV) at the C s (N 1s) ionization thresholds reveals vibrational structures in the spectra. Detailed ab initio and density functional theory (DFT) calculations were performed to interpret the experimental spectra and to assign the observed peaks. In particular we focused on the previously unexplained intensity ratio for the two components of the C1s -->1 pi* transition. For this transition the vibrational structure is included through a linear coupling model in the DFT calculations and leads to the experimentally observed similar to2:3 intensity ratio between the two pi* components in the C1s spectrum rather than the similar to3:2 ratio obtained without vibrational effects. After inclusion of relaxation effects in the excited states, in addition to the vibrational effects, both theoretical methods yield almost perfect agreement with experiment.
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