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| 3. |
- 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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| 4. |
- Carniato, S., et al.
(författare)
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Photon-energy dependence of single-photon simultaneous core ionization and core excitation in CO2
- 2016
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Ingår i: PHYSICAL REVIEW A. - 2469-9926. ; 94:1
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Céolin, A, et al.
(författare)
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Study of the Dissociation of Nitrous Oxide Following Resonant Excitation of the Nitrogen and Oxygen K-shells
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:2, s. 024306-
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Tidskriftsartikel (refereegranskat)abstract
- A photochemistry study on nitrous oxide making use of site-selective excitation of terminal nitrogen, central nitrogen, and oxygen 1s -> 3 pi excitations is presented. The resonant Auger decay which takes place following excitation can lead to dissociation of the N2O+ ion. To elucidate the nuclear dynamics, energy-resolved Auger electrons were detected in coincidence with the ionic dissociation products, and a strong dependence of the fragmentation pathways on the core-hole site was observed in the binding energy region of the first satellite states. A description based on the molecular orbitals as well as the correlation between the thermodynamical thresholds of ion formation and the first electronic states of N2O+ has been used to qualitatively explain the observed fragmentation patterns.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Goldsztejn, G., et al.
(författare)
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Electronic-state-lifetime interference in the hard-x-ray regime : Argon as a showcase
- 2017
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Ingår i: PHYSICAL REVIEW A. - : AMER PHYSICAL SOC. - 2469-9926. ; 95:1
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Tidskriftsartikel (refereegranskat)abstract
- Electronic-state-lifetime interference is a phenomenon specific for ionization of atoms and molecules in the hard-x-ray regime. Using resonant KL2,3L2,3 Auger decay in argon as a showcase, we present a model that allows extracting the interference terms directly from the cross sections of the final electronic states. The analysis provides fundamental information on the excitation and decay processes such as probabilities of various decay paths and the values of the dipole matrix elements for transitions to the excited states. Our results shed light on the interplay between spectator, shake-down, and shake-up processes in the relaxation of deep core-hole states.
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| 10. |
- 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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