SwePub - sökning: WFRF:(Journel L)

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1.	Jahnke, T., et al. (författare) Inner-Shell-Ionization-Induced Femtosecond Structural Dynamics of Water Molecules Imaged at an X-Ray Free-Electron Laser 2021 Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 11:4 Tidskriftsartikel (refereegranskat)abstract The ultrafast structural dynamics of water following inner-shell ionization is a crucial issue in high-energy radiation chemistry. We have exposed isolated water molecules to a short x-ray pulse from a free-electron laser and detected momenta of all produced ions in coincidence. By combining experimental results and theoretical modeling, we can image dissociation dynamics of individual molecules in unprecedented detail. We reveal significant molecular structural dynamics in H2O2+, such as asymmetric deformation and bond-angle opening, leading to two-body or three-body fragmentation on a timescale of a few femtoseconds. We thus reconstruct several snapshots of structural dynamics at different time intervals, which highlight dynamical patterns that are relevant as initiating steps of subsequent radiation-damage processes.
2.	Carniato, S., et al. (författare) Photon-energy dependence of single-photon simultaneous core ionization and core excitation in CO2 2016 Ingår i: PHYSICAL REVIEW A. - 2469-9926. ; 94:1 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.
3.	Carniato, S., et al. (författare) Thomson-resonant interference effects in elastic x-ray scattering near the Cl K edge of HCl 2012 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:9, s. 094311- Tidskriftsartikel (refereegranskat)abstract We experimentally observed interference effects in elastic x-ray scattering from gas-phase HCl in the vicinity of the Cl Kedge. Comparison to theory identifies these effects as interference effects between non-resonant elastic Thomson scattering and resonant Raman scattering. The results indicate the non-resonant Thomson and resonant Raman contributions are of comparable strength. The measurements also exhibit strong polarization dependence, allowing an easy identification of the resonant and non-resonant contributions.
4.	Guillemin, R., et al. (författare) Photoelectron-Auger-electron angular-momentum transfer in core-ionized Ar : Beyond the standard post-collision-interaction model 2019 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 99:6 Tidskriftsartikel (refereegranskat)abstract Electron-ion coincidence experimental data obtained following argon 1s photoionization are reported. Slow photoelectrons were measured in coincidence with Ar+ and Ar2+ ions, and the beta angular distribution parameter was obtained. The measured beta parameter for the Ar2+-photoelectron coincidence measurements shows a significant deviation from the beta = 2 expected value. With the support of a quantum mechanical theory of post-collision interaction (PCI) which goes beyond the standard model, we attribute this deviation to angular-momentum exchange due to the interaction of the photoelectron with the Auger electron, while the role of the residual ion is negligible. The main mechanism of angular-momentum transfer and its effect on the asymmetry parameter beta near the photoionization threshold are considered.
5.	Kosugi, S., et al. (författare) Postcollision-interaction effects in multistep Auger transitions following Ar 1s photoionization 2022 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 106:3 Tidskriftsartikel (refereegranskat)abstract Postcollision-interaction (PCI) effects involving multistep decay processes following Ar 1s photoionization has been studied by Auger electron spectroscopy. The experiment focused on LMM Auger electrons measured in small photon energy steps across the Ar 1s photoionization threshold. Decay pathways that we studied include (1) the Ar+2p-1 -> Ar2+3p-2 LMM alpha Auger process due to a single L hole created by KL fluorescence, (2) the Ar2+2p-2 -> Ar3+2p-13p-2 LMM1 Auger process following double L shell hole states produced by a KLL Auger processes, and (3) the subsequent Ar3+2p-13p-2 -> Ar4+3p-4 LMM2 Auger transitions. Particularly pronounced PCI shifts and unusual line shapes compared to the ordinary one-step PCI process were found in the spectra of Auger processes following a KLL Auger first step. The experimental results were compared with calculations based on the semiclassical approach to PCI. Good agreement was found between the calculated and experimental PCI shifts. The result opens possibilities for further studies of the multielectron dynamics between Auger electrons mediated through the photoelectron in these and similar systems.
6.	Koulentianos, Dimitris, 1987, et al. (författare) Double-core-hole states in CH3CN: Pre-edge structures and chemical-shift contributions 2018 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149 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.
7.	Marchenko, T., et al. (författare) Ultrafast nuclear dynamics in the doubly-core-ionized water molecule observed via Auger spectroscopy 2018 Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 98:6 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.
8.	Martins, J. B., et al. (författare) Electron delocalisation in conjugated sulfur heterocycles probed by resonant Auger spectroscopy 2022 Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:14, s. 8477-8487 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.
9.	Puttner, R., et al. (författare) Argon 1s(-2) Auger hypersatellites 2020 Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:2 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.
10.	Püttner, R., et al. (författare) Nonstatistical behavior of the photoionization of spin-orbit doublets 2021 Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 54:8 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.
11.	Travnikova, O., et al. (författare) Energy dependent relative cross sections in carbon 1s photoionization 2020 Ingår i: 31ST INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS (ICPEAC XXXI). - : IOP PUBLISHING LTD. Konferensbidrag (refereegranskat)abstract We demonstrate that the possibility of monitoring relative photoionization cross sections over a large photon energy range extending to hard x-rays allows studying and disentangling shake processes and intramolecular inelastic scattering effects. An "EXAFS"-type of oscillatory behaviour of the relative C is cross sections is observed in a wide photon energy range up to 1 keV due to multiple intramolecular elastic scattering of the photoelectron. These effects are also present in solids and constitute a significant part of all elastic and inelastic scattering effects occurring in solids.
12.	Allum, Felix, et al. (författare) Coulomb explosion imaging of CH3I and CH2CII photodissociation dynamics 2018 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149:20 Tidskriftsartikel (refereegranskat)abstract The photodissociation dynamics of CH3I and CH2CII at 272 nm were investigated by time-resolved Coulomb explosion imaging, with an intense non-resonant 815nmprobe pulse. Fragment ion momenta over a widem/z range were recorded simultaneously by coupling a velocity map imaging spectrometer with a pixel imaging mass spectrometry camera. For both molecules, delay-dependent pump-probe features were assigned to ultraviolet-induced carbon-iodine bond cleavage followed by Coulomb explosion. Multi-mass imaging also allowed the sequential cleavage of both carbon-halogen bonds in CH2ClI to be investigated. Furthermore, delay-dependent relative fragment momenta of a pair of ions were directly determined using recoil-frame covariance analysis. These results are complementary to conventional velocity map imaging experiments and demonstrate the application of time-resolved Coulomb explosion imaging to photoinduced real-time molecular motion.
13.	Bomme, C., et al. (författare) Molecular-frame photoelectron angular distribution imaging studies of OCS S1s photoionization 2012 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 45:19, s. 194005- Tidskriftsartikel (refereegranskat)
14.	Bomme, C., et al. (författare) Post-collision interaction manifestation in molecular systems probed by photoelectron-molecular ion coincidences 2013 Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:21, s. 215101- Tidskriftsartikel (refereegranskat)abstract S1s photoionization in carbonyl sulfide (OCS), followed by multiple Auger decay is investigated both experimentally and theoretically, by means of photoelectron-ion coincidences. A strong influence of post-collision interaction is observed in the energy shift and the distortion of the photoelectron spectra. The magnitude of this effect depends on the total charge of the ionic fragments, i.e., on the number of electrons emitted during the decay of the inner vacancy. A satisfactory agreement is found between experiment and theory, which allows us to estimate the lifetimes of the various two-hole states of the intermediate OCS2+ ion.
15.	Boudjemia, N., et al. (författare) Deep-core photoionization of krypton atoms below and above the 1s ionization threshold 2020 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 101:5 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.
16.	Boudjemia, N., et al. (författare) Electron spectroscopy and dynamics of HBr around the Br 1s(-1) threshold 2020 Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:46, s. 26806-26818 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.
17.	Brasse, Felix, et al. (författare) Time-resolved inner-shell photoelectron spectroscopy : From a bound molecule to an isolated atom 2018 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 97:4 Tidskriftsartikel (refereegranskat)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.
18.	Burt, Michael, et al. (författare) Coulomb-explosion imaging of concurrent CH2BrI photodissociation dynamics 2017 Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 96:4 Tidskriftsartikel (refereegranskat)abstract The dynamics following laser-induced molecular photodissociation of gas-phase CH2BrI at 271.6 nm were investigated by time-resolved Coulomb-explosion imaging using intense near-IR femtosecond laser pulses. The observed delay-dependent photofragment momenta reveal that CH2BrI undergoes C-I cleavage, depositing 65.6% of the available energy into internal product states, and that absorption of a second UV photon breaks the C-Br bond of C(H)2Br. Simulations confirm that this mechanism is consistent with previous data recorded at 248 nm, demonstrating the sensitivity of Coulomb-explosion imaging as a real-time probe of chemical dynamics.
19.	Carniato, S., et al. (författare) A new method to derive electronegativity from resonant inelastic x-ray scattering 2012 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:14, s. 144303- Tidskriftsartikel (refereegranskat)abstract Electronegativity is a well-known property of atoms and substituent groups. Because there is no direct way to measure it, establishing a useful scale for electronegativity often entails correlating it to another chemical parameter; a wide variety of methods have been proposed over the past 80 years to do just that. This work reports a new approach that connects electronegativity to a spectroscopic parameter derived from resonant inelastic x-ray scattering. The new method is demonstrated using a series of chlorine-containing compounds, focusing on the Cl 2p(-1)LUMO(1) electronic states reached after Cl 1s -> LUMO core excitation and subsequent KL radiative decay. Based on an electron-density analysis of the LUMOs, the relative weights of the Cl 2p(z) atomic orbital contributing to the Cl 2p(3/2) molecular spin-orbit components are shown to yield a linear electronegativity scale consistent with previous approaches.
20.	Carniato, S., et al. (författare) K-L resonant X-ray Raman scattering as a tool for potential energy surface mapping 2007 Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 439:06-apr, s. 402-406 Tidskriftsartikel (refereegranskat)abstract With help of theoretical calculations, we demonstrate that original pump-probe experiments, using IR laser as a pump and K-L X-ray Raman scattering as a probe, offer a powerful tool to map core-excited potential energy curves with very high energy resolution, beyond vibrational and lifetime limitations.
21.	Ceolin, D., et al. (författare) Auger resonant-Raman study at the Ar K edge as probe of electronic-state-lifetime interferences 2015 Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:2 Tidskriftsartikel (refereegranskat)abstract The resonant-Auger decay in argon following Ar 1s - np excitations was studied under resonant-Raman conditions, i.e., with a total instrumental bandwidth much narrower than the natural linewidth of the absorption features. These state-of-the-art experiments are combined with a radiationless resonant-Raman scattering theory. The main results include identification of the energy position of some high-lying Rydberg states previously masked by insufficient resolution and clear evidence of electronic-state-lifetime interference phenomena.
22.	Feifel, Raimund, et al. (författare) Cationic double K-hole pre-edge states of CS2 and SF6 2017 Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7 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.
23.	Goldsztejn, G., et al. (författare) Double-Core-Hole States in Neon: Lifetime, Post-Collision Interaction, and Spectral Assignment 2016 Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:13 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.
24.	Goldsztejn, G., et al. (författare) Electronic-state-lifetime interference in the hard-x-ray regime : Argon as a showcase 2017 Ingår i: PHYSICAL REVIEW A. - : AMER PHYSICAL SOC. - 2469-9926. ; 95:1 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.
25.	Goldsztejn, G., 2017, et al. (författare) Experimental and theoretical study of the double-core-hole hypersatellite Auger spectrum of Ne 2017 Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 96 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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