| 1. |
- Velasquez, Nicolas, et al.
(författare)
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Generalization of the post-collision interaction effect from gas-phase to solid-state systems demonstrated in thiophene and its polymers
- 2023
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Ingår i: Physical Review Research. - : American Physical Society. - 2643-1564. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate experimentally and theoretically the presence of the post-collision interaction (PCI) effect in sulfur KL2,3L2,3 Auger electron spectra measured in the gas-phase thiophene and in solid-state organic polymers: polythiophene (PT) and poly(3-hexylthiophene-2,5-diyl), commonly known as P3HT. PCI manifests itself through a distortion and a blueshift of the normal Auger S KL2,3L2,3 spectrum when S 1s ionization occurs close to the ionization threshold. Our investigation shows that the PCI-induced shift of the Auger spectra is stronger in the solid-state polymers than in the gas-phase organic molecule. Theoretical modeling within the framework of the eikonal approximation provides good agreement with the experimental observations. In a solid medium, two effects influence the interaction between the photoelectron and the Auger electron. In detail, stronger PCI in the polymers is attributed to the photoelectron scattering in the solid, which overcompensates the polarization screening of electron charges which causes a reduction of the interaction. Our paper demonstrates the general nature of the PCI effect occurring in different media.
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| 2. |
- Allum, Felix, et al.
(författare)
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Coulomb explosion imaging of CH3I and CH2CII photodissociation dynamics
- 2018
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149:20
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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.
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| 3. |
- Bao, Zhuo, et al.
(författare)
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Detailed Theoretical and Experimental Description of Normal Auger Decay in O2
- 2008
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 41:12, s. 125101-
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Tidskriftsartikel (refereegranskat)abstract
- The normal Auger electron spectrum of the O-2 molecule is assigned in detail on the basis of ab initio valence configuration interaction (CI) wavefunctions. Potential energy curves of the ground state, the core-ionized states and the doubly charged final states are calculated and Auger decay rates are obtained with the one-centre approximation. Using the lifetime vibrational interference method, band shapes are obtained for all contributions to the Auger spectrum. The calculated Auger electron spectrum allows us to identify all features observed experimentally. Significant differences to previous assignments are reported. A quantitative simulation of the spectrum is given on the basis of a curve-fitting procedure, in which the energetic positions and intensities of the theoretical bands were optimized. Besides providing a basis for a refined analysis of the spectrum, the fit allows us to assess the accuracy of the calculation. As expected for this level of theory, the absolute accuracy of the valence CI energies is found to be about 0.3 eV. The inherent error of the one-centre transition rates is less than 5% of the most intense transition in the spectrum. The frequently questioned one-centre Auger transition rates are shown to be rather appropriate if applied with reasonable wavefunctions and if the vibrational band structure of the molecular spectrum is properly taken into account.
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| 4. |
- Bao, Zhuo, 1977-
(författare)
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Synchrotron Radiation Studies of Free and Adsorbed Molecules
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contains two parts. The first part concerns the research work on free molecules using synchrotron-radiation-related techniques. Auger electron spectra of two free open-shell molecules, O2 and NO, were studied experimentally and theoretically. Photoionization experimental technique with tunable synchrotron radiation source was used to induce core-level electron ionization and obtain the KVV normal Auger electron spectra. A quantitative assignment of O2 normal Auger spectrum was obtained by applying ab initio CI calculations and LVI Auger line shape simulations including the bond length dependence of Auger transition rates. The photon energy dependence of normal Auger electron spectra was focused on with photon energies in the vicinities of core-ionization threshold energies. Consequently, the MAPCI (Molecular Auger Post Collision Interaction) theory was developed. Taking the near-threshold O2 normal Auger spectrum as an example, the two extreme cases of MAPCI effect, “atomic-like PCI” and “molecular PCI”, were discovered and discussed. The effect of shape resonance on near-threshold molecular normal Auger spectrum was discussed taking NO near threshold normal Auger spectra as example.The second part deals with research work on the chemisorption of small epoxy organic molecules, ethylene oxide, methyl oxirane, on Si (100) surfaces. Synchrotron radiation related techniques, UPS, XPS and NEXAFS, were applied. Based on the valence photoemission spectra, C 1s and Si 2p XPS spectra, the epoxy ring opening reactions of these molecules in chemisorption process were proved. Further tentative search for the surface-adsorbate CDAD effect was performed, and no evident circular dichroism was confirmed.
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| 5. |
- Bolognesi, P., et al.
(författare)
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A study of the dynamical energy flow in uracil
- 2015
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- The time resolved photoionization of C 1s in uracil following excitation of the neutral molecule by 260 nm pulses has been studied at LCLS.
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| 6. |
- Bomme, C., et al.
(författare)
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Post-collision interaction manifestation in molecular systems probed by photoelectron-molecular ion coincidences
- 2013
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:21, s. 215101-
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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.
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| 7. |
- Boudjemia, Nacer, et al.
(författare)
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Deep core photoionization of iodine in CH3I and CF3I molecules : how deep down does the chemical shift reach?
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21:10, s. 5448-5454
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Tidskriftsartikel (refereegranskat)abstract
- Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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| 11. |
- Bowen, K. P., et al.
(författare)
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Nondipole Effects in Chiral Molecules Measured with Linearly Polarized Light
- 2015
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- We present the first-ever measurement of nondipole chiral angular distribution parameters for C 1s photoemission from each enantiomer of camphor in the photon energy range 296-343eV using linearly polarized light. The angular distribution parameters are determined to be enantiomer-specific, suggesting a new form of linear dichroism.
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| 12. |
- Brasse, Felix, et al.
(författare)
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Time-resolved inner-shell photoelectron spectroscopy : From a bound molecule to an isolated atom
- 2018
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 97:4
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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.
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| 13. |
- Burt, Michael, et al.
(författare)
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Coulomb-explosion imaging of concurrent CH2BrI photodissociation dynamics
- 2017
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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.
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| 14. |
- Capron, Nathalie, et al.
(författare)
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Correction: Probing keto–enol tautomerism using photoelectron spectroscopy
- 2018
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:1, s. 695-695
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Tidskriftsartikel (refereegranskat)abstract
- Correction for ‘Probing keto–enol tautomerism using photoelectron spectroscopy’ by Nathalie Capron et al., Phys. Chem. Chem. Phys., 2015, 17, 19991–19996.
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| 15. |
- Capron, Nathalie, et al.
(författare)
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Probing keto-enol tautomerism using photoelectron spectroscopy
- 2015
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 17:30, s. 19991-19996
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically investigate the mechanism of tautomerism in the gas-phase acetylacetone molecule. The minimum energy path between the enolone and diketo forms has been computed using the Nudged-Elastic Band (NEB) method within the density-functional theory (DFT) using the projector augmented-wave method and generalized gradient approximation in Perdew-Wang (PW91) parametrization. The lowest transition state as well as several intermediate geometries between the two stable tautomers have been identified. The outer-valence ionization spectra for all determined geometries have been computed using the third-order non-Dyson algebraic diagrammatic construction technique. Furthermore, the oxygen core-shell ionization spectra for these geometries have been obtained using DFT and the Becke three-parameter Lee-Yang-Parr (B3LYP) functional. It is shown that all spectra depend strongly on the geometries demonstrating the possibility of following the proton-transfer dynamics using photoelectron spectroscopy in pump-probe experiments.
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| 16. |
- Carniato, S., et al.
(författare)
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A new method to derive electronegativity from resonant inelastic x-ray scattering
- 2012
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:14, s. 144303-
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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.
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| 17. |
- 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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| 18. |
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| 19. |
- Céolin, Denis, et al.
(författare)
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A rotatable electron spectrometer for multicoincidence experiments
- 2010
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 81:6
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Tidskriftsartikel (refereegranskat)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]
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| 20. |
- Ceolin, D., et al.
(författare)
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Auger resonant-Raman study at the Ar K edge as probe of electronic-state-lifetime interferences
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 91:2
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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.
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| 21. |
- Ceolin, Denis, et al.
(författare)
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Effect of the Cl2p core orbital excitation on the nuclear dynamics of the three dichloroethylene isomers
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 184:1-2, s. 24-28
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we present the X-ray absorption spectra of the three isomers of dichloroethylene C2H2Cl2 in the vicinity of the chlorine L-2 and L-3 edges. These isomers were excited along the first Cl2p to lowest unoccupied molecular orbital transition and an analysis of the corresponding resonant Auger spectra shows that the C-Cl bond can break before the electronic decay. An investigation of a possible Auger Doppler-like effect is also presented.
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| 22. |
- Ceolin, Denis, et al.
(författare)
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Fragmentation of methyl chloride studied by partial positive and negative ion-yield spectroscopy
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 126:8, s. 084309-
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Tidskriftsartikel (refereegranskat)abstract
- The authors present partial-ion-yield experiments on the methyl chloride molecule excited in the vicinity of the C12p and C1s inner shells. A large number of fragments, cations produced by dissociation or recombination processes, as well as anionic species, have been detected. Although the spectra exhibit different intensity distributions depending on the core-excited atom, general observations include strong site-selective fragmentation along the C-Cl bond axis and a strong intensity dependence of transitions involving Rydberg series on fragment size.
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| 23. |
- Céolin, Denis, et al.
(författare)
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Recoil-induced ultrafast molecular rotation probed by dynamical rotational Doppler effect
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Observing and controlling molecular motion, and in particular rotation,is a fundamental topic in physics and chemistry. In order toinitiate ultrafast rotation, one needs a way to transfer a large angularmomentum to the molecule. As a showcase, this was performedby hard x-ray C1s ionization of carbon monoxide, accompanied byspinning-up the molecule via the recoil “kick” of the emitted fast photoelectron.To visualize this molecular motion, we use the dynamicalrotational Doppler effect and an X-ray “pump-probe” device offeredby nature itself: the recoil-induced ultrafast rotation is probed by subsequentAuger electron emission. The time information in our experimentorigins from the natural delay between the C1s photoionizationinitiating the rotation and the ejection of the Auger electron. From amore general point of view, time-resolved measurements can be performedin two ways: either to vary the "delay" time as in conventionaltime-resolved pump-probe spectroscopy and to use the dynamicsgiven by the system, or to keep constant "delay" time and to manipulatethe dynamics. Since in our experiment we cannot change the delaytime given by the core-hole lifetime $\tau$, we use the second optionand control the rotational speed by changing the kinetic energy of thephotoelectron. The recoil-induced rotational dynamics controlled insuch a way is observed as a photon-energy dependent asymmetryof the Auger lineshape, in full agreement with theory. This asymmetryis explained by a significant change of the molecular orientationduring the core-hole lifetime, which is comparable with the rotationalperiod.
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| 24. |
- Ceolin, Denis, et al.
(författare)
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Recoil-induced ultrafast molecular rotation probed by dynamical rotational Doppler effect
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 116:11, s. 4877-4882
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Tidskriftsartikel (refereegranskat)abstract
- Observing and controlling molecular motion and in particular rotation are fundamental topics in physics and chemistry. To initiate ultrafast rotation, one needs a way to transfer a large angular momentum to the molecule. As a showcase, this was performed by hard X-ray C1s ionization of carbon monoxide accompanied by spinning up the molecule via the recoil "kick" of the emitted fast photoelectron. To visualize this molecular motion, we use the dynamical rotational Doppler effect and an X-ray "pump-probe" device offered by nature itself: the recoil-induced ultrafast rotation is probed by subsequent Auger electron emission. The time information in our experiment originates from the natural delay between the C1s photoionization initiating the rotation and the ejection of the Auger electron. From a more general point of view, time-resolved measurements can be performed in two ways: either to vary the "delay" time as in conventional time-resolved pump-probe spectroscopy and use the dynamics given by the system, or to keep constant delay time and manipulate the dynamics. Since in our experiment we cannot change the delay time given by the core-hole lifetime tau, we use the second option and control the rotational speed by changing the kinetic energy of the photoelectron. The recoil-induced rotational dynamics controlled in such a way is observed as a photon energy-dependent asymmetry of the Auger line shape, in full agreement with theory. This asymmetry is explained by a significant change of the molecular orientation during the core-hole lifetime, which is comparable with the rotational period.
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| 25. |
- Ceolin, Denis, et al.
(författare)
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Site-selective resonant Auger spectroscopy of iso-dichloroethylene at the carbon K-edge
- 2012
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 185:8-9, s. 252-258
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the two C1s-to-LUMO (lowest unoccupied molecular orbital) excitations of the iso-dichloroethylene (H2C=CCl2) and the subsequent Auger decay. We investigate the effect of the two different carbon core excitations on the population of the cation produced after electronic relaxation. The resonant Auger spectra are interpreted by comparison to the valence shells photoionization spectrum and with the help of theoretical calculations. Several consequences of the core-hole localization on the electronic decay are observed. In particular, the resonant excitation of the C1s(CH2) to the LUMO leads to a large intensity increase in the region of the first satellite state, whereas no dramatic changes are observed for the C1s(CCl2) excitation.
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| 26. |
- Decleva, Piero, et al.
(författare)
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Interference effects in photoelectron asymmetry parameter (beta) trends of C 2s(-1) states of ethyne, ethene and ethane
- 2016
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:23
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron asymmetry parameters (beta) of the gerade and ungerade C 2s(-1) derived states of ethyne, ethene and ethane as a function of photon energy have been calculated and experimentally measured, to extend the search of interference effects on angular distributions to polyatomic molecules. The calculations cover the electron energy range from 0 to 1100 eV while the experimental measurements cover the electron energy range from 30 to 220 eV. Clear oscillations are interpreted in terms of interference of the photoelectron wave emitted from the two possible C 2s centres, or equivalently from the gerade and ungerade states associated with them. This is a microscopic analog of Young's double-slit experiment. The effect is however quite small and requires very high experimental accuracy to be detected. It is best evidenced in the behaviour of beta difference between the two channels. The connection between beta trends and structural parameters shows the expected inverse correlation between oscillation period and distance between the carbon atoms, but do not simply parallel the analogous behaviour found in cross sections.
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| 27. |
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| 28. |
- 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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| 29. |
- Feifel, Raimund, et al.
(författare)
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Core-level spectroscopy and dynamics of free molecules
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 183:1-3, s. 10-28
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Tidskriftsartikel (refereegranskat)abstract
- A review of recent results on spectroscopy and dynamics of free molecules is presented. The experimental research reported here is mainly concerned with processes of core excitation and decay of isolated molecules, primarily investigated by resonant Auger spectroscopy. Several examples are shown concerning the interplay of the timescales of electron decay with nuclear motion involving dissociation processes, the occurrence of interference phenomena and recoil. The capability of such studies to reveal subtle details of the light-matter interaction, of the electronic structure and of the evolution of the short-lived states thus created is enlightened.
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| 30. |
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| 31. |
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| 32. |
- Feifel, Raimund, et al.
(författare)
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Interference Quenching of v
- 2002
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Ingår i: Physical Review Letters. ; 89:10, s. 103002-1
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Tidskriftsartikel (refereegranskat)
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| 33. |
- Feifel, Raimund, et al.
(författare)
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Probing the valence character of O-1s -> Rydberg excited O-2 by participator Auger decay measurements and partial ion yield spectroscopy following x-ray absorption
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 126:17, s. 174304-
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Tidskriftsartikel (refereegranskat)abstract
- The valence character of O 1s -> Rydberg excited O-2 is investigated by means of participator Auger decay spectroscopy, performed at selected photon energies across the K-shell resonance region, and by means of partial ion yield x-ray absorption spectroscopy. For several of the excitation energies studied, the authors find substantial sigma(*)((4)Sigma(-)(u),(2)Sigma(-)(u)) valence character being mixed with ns sigma and np sigma ((4)Sigma(-)(u),(2)Sigma(-)(u)) Rydberg states. An experimental indication of a coupling between the channels associated with quartet and doublet ion cores is considered and discussed. New spectroscopic constants are derived for the singly ionized X (2)Pi(g) state of O-2 based on the observation of at least 20 vibrational sublevels.
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| 34. |
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| 35. |
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| 36. |
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| 37. |
- Fink, Reinhold, et al.
(författare)
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Specific production of very long-lived core-excited sulfur atoms by 2p(-1)sigma* excitation of the OCS molecule followed by ultrafast dissociation
- 2006
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Ingår i: Journal of Physics B. - 0953-4075 .- 1361-6455. ; 39:12, s. L269-L275
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Tidskriftsartikel (refereegranskat)abstract
- A core-excited sulfur state with a lifetime almost one order of magnitude longer than in molecular 2p core-hole states is selectively produced by ultrafast dissociation of S 2p -> sigma* excited OCS. Clear evidence for this is provided by strong atomic peaks (20% of the total intensity) in x-ray fluorescence but very weak ones (2%) in the corresponding resonant Auger spectrum. Corroborating the assignment of the spectra, ab initio calculations explain the enhanced lifetime: the Auger decay of the produced D-3(3) (2p(5)3p(5)) sulfur state is strongly decreased as it contradicts a newly derived propensity rule of the L2,3MM Auger decay.
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| 38. |
- Frasinski, L. J., et al.
(författare)
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Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:7, s. 073002-
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Tidskriftsartikel (refereegranskat)abstract
- When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called partial covariance mapping'' to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.
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| 39. |
- Goldsztejn, Gildas, et al.
(författare)
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Electronic state-lifetime interference in resonant Auger spectra : a tool to disentangle overlapping core-excited states
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:22, s. 15133-15142
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Tidskriftsartikel (refereegranskat)abstract
- We have measured resonant-Auger decay following Cl 1s(-1) excitations in HCl and CH3Cl molecules, and extracted the pseudo-cross sections of different Cl 2p(-2) final states. These cross sections show clear evidence of shake processes as well as contributions of electronic state-lifetime interference (ELI). To describe the spectra we developed a fit approach that takes into account ELI contributions and ultrafast nuclear dynamics in dissociative core-excited states. Using this approach we utilized the ELI contributions to obtain the intensity ratios of the overlapping states Cl 1s(-1)4p pi/1s(-1)4p sigma in HCl and Cl 1s(-1)4pe/1s(-1)4pa(1) in CH3Cl. The experimental value for HCl is compared with theoretical results showing satisfactory agreement.
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| 40. |
- 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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| 41. |
- 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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| 42. |
- Goldsztejn, G., et al.
(författare)
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Simulation of Auger decay dynamics in the hard X-ray regime : HCl as a showcase
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:11, s. 6590-6604
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Tidskriftsartikel (refereegranskat)abstract
- Auger decay after photoexcitation or photoemission of an electron from a deep inner shell in the hard X-ray regime can be rather complex, implying a multitude of phenomena such as multiple-step cascades, post-collision interaction (PCI), and electronic state-lifetime interference. Furthermore, in a molecule nuclear motion can also be triggered. Here we discuss a comprehensive theoretical method which allows us to analyze in great detail Auger spectra measured around an inner-shell ionization threshold. HCl photoexcited or photoionized around the deep Cl 1s threshold is chosen as a showcase. Our method allows calculating Auger cross sections considering the nature of the ground, intermediate and final states (bound or dissociative), and the evolution of the relaxation process, including both electron and nuclear dynamics. In particular, we show that we can understand and reproduce a so-called experimental 2D-map, consisting of a series of resonant Auger spectra measured at different photon energies, therefore obtaining a detailed picture of all above-mentioned dynamical phenomena at once.
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| 43. |
- Goldsztejn, G., et al.
(författare)
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Ultrafast Dynamics And Electronic State - Lifetime Interferences In Chlorine-Containing Molecules
- 2015
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- In order to have access to fine phenomena such as ultrafast nuclear dynamics and electronic state - lifetime interferences (ELI) at high energies (few keV), one has to rely on great experimental resolution. The new experimental HAXPES endstation at the GALAXIES beamline of the French synchrotron SOLEIL provides photons in the 2-12 keV energy range along with a total instrumental resolution below 500 meV. In this work we show experimental evidences of ultrafast nuclear dynamics and ELI on HCl and CH3Cl excited around the Cl 1s resonance. We show also simulations that allow to disentangle the contribution of nuclear dynamics and ELI in our experimental spectra.
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| 44. |
- Guillemin, Renaud, et al.
(författare)
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A review of molecular effects in gas-phase KL X-ray emission
- 2013
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 188, s. 53-61
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Forskningsöversikt (refereegranskat)abstract
- The unique capabilities of resonant inelastic X-ray scattering (RIXS) to provide a deep insight into molecular dynamics following core excitation are reviewed here. Characteristic features of molecular X-ray emission are experimentally observed and theoretically interpreted. Some of our most significant results on molecular dynamics following deep core excitation are presented. In particular, we provide several examples of nuclear dynamics on the femtosecond or subfemtosecond time scale; line-narrowing effects related to the quenching of vibrational structure due to parallelism of intermediate and final state curves; anomalous line dispersion across a resonance, which is due to core-hole lifetime effects; spin–orbit-state populations derived from polarized RIXS experiments. We also show how to connect the RIXS results to the general chemical properties of the investigated systems.
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| 45. |
- Guillemin, Renaud, et al.
(författare)
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Angular and dynamical properties in resonant inelastic x-ray scattering : Case study of chlorine-containing molecules
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Polarization-dependent resonant inelastic x-ray scattering (RIXS) has been shown to be a probe of molecular-field effects on the electronic structure of isolated molecules. In this experimental analysis we explain the linear dichroism observed in Cl 2p polarized RIXS following Cl 1s excitation of a series of chlorofluoromethanes (CF3Cl, CF2Cl2, CFCl3, and CCl4) as due to molecular-field effects, including singlet-triplet exchange. We present an approach to extract directly the 2p inner-shell electronic state populations from the experimental measurements. Using the angular properties of the measured KV emission we also are able to determine the value of the polarization anisotropy parameter beta(p) for each resolved component of the KV emission spectra.
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| 46. |
- Guillemin, Renaud, et al.
(författare)
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Complex decay patterns in atomic core photoionization disentangled by ion-recoil measurements
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 84:6
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Tidskriftsartikel (refereegranskat)abstract
- Following core 1s ionization and resonant excitation of argon atoms, we measure the recoil energy of the ions due to momentum conservation during the emission of Auger electrons. We show that such ion momentum spectroscopy can be used to disentangle to some degree complex decay patterns, involving both radiative and nonradiative decays.
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| 47. |
- Guillemin, R., et al.
(författare)
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Concerted and sequential three-body fragmentation of deep-core-ionized carbon disulfide
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:1, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- Momentum vector correlation is a powerful tool to study molecular dissociation. We have studied the three-body fragmentation of carbon disulfide after sulfur 1s photoionization by means of momentum imaging techniques. Concerted and sequential pathways are disentangled in three-body fragmentation using adapted analysis strategies. In particular, we introduce various data visualization schemes that are proved to be particularly efficient to determine dissociation dynamics.
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| 48. |
- Guillemin, R., et al.
(författare)
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Interplay of complex decay processes after argon 1s ionization
- 2018
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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. ; 97:1
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Tidskriftsartikel (refereegranskat)abstract
- Complex decay pathways involving radiative and nonradiative relaxation after deep core-level ionization in argon are disentangled by a unique combination of several synchrotron radiation-based spectroscopic techniques. In particular, by comparing the results obtained from electron-ion coincidence, photon-ion coincidence, and x-ray emission measurements, we are able to distinguish the final ionic states produced in the cascade decay involving K alpha and K beta radiative decay and final ionic states produced by nonradiative cascade decay. High-resolution Auger electron spectroscopy is then used as a complementary tool to identify the LMM transitions contributing to the cascade decay. Ab initio calculations are performed to identify the electronic states involved in the LMM decay.
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| 49. |
- Guillemin, Renaud, et al.
(författare)
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Jahn-Teller coupling and fragmentation after core-shell excitation in CF4 investigated by partial-ion-yield spectroscopy
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:4, s. 043427-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate fragmentation processes induced by core-level photoexcitation in CF4 at both the carbon and fluorine K edges by means of partial-ion-yield spectroscopy. The molecule CF4 is a textbook example of systems in which Jahn-Teller coupling strongly manifests itself in the photoabsorption spectrum. Spectral features related to Jahn-Teller and quasi-Jahn-Teller splitting are observed, and important differences in the fragmentation pathways are revealed depending on the symmetries of the core-excited states. We interpret these experimental observations on the grounds of symmetry lowering from the T-d to the C-3v point group as well as preferential orientation with respect to the polarization vector of the incident radiation.
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| 50. |
- Guillemin, R., et al.
(författare)
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Photoelectron-Auger-electron angular-momentum transfer in core-ionized Ar : Beyond the standard post-collision-interaction model
- 2019
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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. ; 99:6
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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.
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