| 1. |
- Guillemin, R., et al.
(författare)
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Selecting core-hole localization or delocalization in CS2 by photofragmentation dynamics
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Electronic core levels in molecules are highly localized around one atomic site. However, in single-photon ionization of symmetric molecules, the question of core-hole localization versus delocalization over two equivalent atoms has long been debated as the answer lies at the heart of quantum mechanics. Here, using a joint experimental and theoretical study of core-ionized carbon disulfide (CS2), we demonstrate that it is possible to experimentally select distinct molecular-fragmentation pathways in which the core hole can be considered as either localized on one sulfur atom or delocalized between two indistinguishable sulfur atoms. This feat is accomplished by measuring photoelectron angular distributions within the frame of the molecule, directly probing entanglement or disentanglement of quantum pathways as a function of how the molecule dissociates.
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| 2. |
- Kokkonen, E., et al.
(författare)
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Formation of stable HCl+ following resonant Auger decay in CH3Cl
- 2016
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Ingår i: PHYSICAL REVIEW A. - : American Physical Society. - 2469-9926. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- Photoinduced reformation of chemical bonds is investigated in the CH3Cl molecule experimentally and computationally. The observation of stable HCl+ fragment formation after resonant Cl 2p photoexcitation is confirmed by an electron-ion coincidence experiment, and its possible creation mechanism is reported. We attribute the formation of HCl+ to specific final states populated by the resonant Auger decay. Quantum chemical computations support this attribution and suggest that in at least one of those states the system is placed on a potential energy surface which favors creation of HCl+ by moving one hydrogen atom to a closer proximity of the chlorine atom. This work demonstrates the effect of targeted core-shell excitation on the chemical bond breaking and reformation process, often called photoinduced chemistry.
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| 3. |
- Kushawaha, R. K., et al.
(författare)
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Auger resonant-Raman decay after Xe L-edge photoexcitation
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 92:1
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated resonant Auger decay of xenon following photoexcitation of each of the three L edges under resonant-Raman conditions, which allowed us to characterize several higher Rydberg transitions. Relative intensities for spectator final states reached after L-1-, L-2-, and L-3-edge excitations are studied in detail. Thanks to state-of-the-art experimental arrangements, our results not only reproduce the previously calculated 3d(-2)5d and nd (n > 5) state cross sections after L-3 excitation, but also allow extracting the 3d(-2)6d spectator state energy position and revealing its resonant behavior, blurred by the insufficient experimental resolution in previous data sets. The 3d(-2)6p and 3d(-2)7p states reached after L-1 excitation as well as the 3d(-2)5d and 3d(-2)6d states reached after L-2 excitation are also investigated and their relative intensities are reported and compared to ab initio Dirac-Hartree-Fock configuration-interaction calculations. We found the signature of electronic-state-lifetime interference effects between several coherently excited intermediate states, due to large lifetime broadening. Electron recapture processes are also identified above all three photoionization thresholds.
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| 4. |
- Marchenko, T., et al.
(författare)
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Potential Energy Surface Reconstruction and Lifetime Determination of Molecular Double-Core-Hole States in the Hard X-Ray Regime
- 2017
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 119:13
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Tidskriftsartikel (refereegranskat)abstract
- A combination of resonant inelastic x-ray scattering and resonant Auger spectroscopy provides complementary information on the dynamic response of resonantly excited molecules. This is exemplified for CH3I, for which we reconstruct the potential energy surface of the dissociative I 3d(-2) double-core-hole state and determine its lifetime. The proposed method holds a strong potential for monitoring the hard x-ray induced electron and nuclear dynamic response of core-excited molecules containing heavy elements, where ab initio calculations of potential energy surfaces and lifetimes remain challenging.
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| 5. |
- Puettner, R., et al.
(författare)
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Detailed assignment of normal and resonant Auger spectra of Xe near the L edges
- 2017
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 96:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive experimental and theoretical investigation on the LMM, LMN, and LNN normal Auger spectra of xenon, which reveal excellent agreement with theory when core-hole lifetimes of the two-hole final states are taken into account. Generally, the spectra turned out to be highly complex due to a strong overlap of the Auger transitions subsequent to 2s(1/2)(-1), 2p(1/2)(-1), and 2p(3/2)(-1) ionization. This overlap is due to the splitting of the three initial L core holes and the different final M and N core holes being on the same order of magnitude of several hundred eV. The Auger transitions are assigned in detail based on the theoretical results. Most of the MM, MN, and NN final states are described well based on jj coupling. In addition, we present a detailed assignment of the resonant LM45M45 Auger transition subsequent to the 2s -> 6p, 7p and 2p -> 5d, 6d excitations.
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| 6. |
- Andersson, T., et al.
(författare)
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Electronic structure transformation in small bare Au clusters as seen by x-ray photoelectron spectroscopy
- 2017
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:1
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Tidskriftsartikel (refereegranskat)abstract
- Free bare gold clusters in the size range from few tens to few hundred atoms (<= 1 nm dimensions) have been produced in a beam, and the size-dependent development of their full valence band including the 5d and 6s parts has been mapped 'on the fly' by synchrotron-based photoelectron spectroscopy. The Au 4f core level has been also probed, and the cluster-specific Au 4f ionization energies have been used to estimate the cluster size. The recorded in the present work valence spectra of the small clusters are compared with the spectra of the large clusters (N similar to 10(3)) created by us using a magnetron-based gas aggregation source. The comparison shows a substantially narrower 5d valence band and the decrease in its splitting for gold clusters in the size range of few hundred atoms and below. Our DFT calculations involving the pseudopotential method show that the 5d band width of the ground state increases with the cluster size and by the size N = 20 becomes comparable with the experimental width of the valence photoelectron spectrum. Similar to the earlier observations on supported clusters we interpret our experimental and theoretical results as due to the undercoordination of a large fraction of atoms in the clusters with N similar to 10(2) and below. The consequences of such electronic structure of small gold clusters are discussed in connection with their specific physical and chemical properties related to nanoplasmonics and nanocatalysis.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- Fritzsche, S., et al.
(författare)
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Photoelectron satellite structure from the 3d and 4d inner-shell ionization of rubidium and cesium: Role of atomic relaxation
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:3
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Tidskriftsartikel (refereegranskat)abstract
- The photoelectron satellite structure of rubidium and cesium has been investigated following the photoionization of an nd (n= 3,4) inner-shell electron. The intensity ratios of the nd(-1) ms monopole and nd(-1) m'p conjugated satellite lines have been measured at MAX-lab by using high-resolution electron spectroscopy. For rubidium, moreover, the energy dependence of the 3d(j)6s/3d(j)5s and 3d(j)5p/3d(j)5s intensity ratios with j=3/2 and 5/2 is measured and compared with multiconfiguration Dirac-Fock calculations. A good or at least reasonable agreement is found for both the monopole and conjugated shake-up probabilities if the relaxation of the bound-state electron density is taken into account in the computation of the photoionization cross sections. It is shown that, for the inner-shell ionization of medium and heavy atoms, the orbital relaxation accounts for a significant part of the satellite structure in the photoelectron spectra.
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| 10. |
- Iablonskyi, D., et al.
(författare)
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3d photoionization and subsequent decay of atomic gallium
- 2013
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:17
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental and theoretical study of 3d photoionization and subsequent Auger decay of atomic gallium. The synchrotron radiation-induced electron spectra have been compared and analysed using multiconfiguration Dirac-Fock calculations. It has been shown that the theoretically predicted photoelectron spectrum is in rather good agreement with the experiment allowing us to identify the main spectral features. However, prediction of the Auger decay intensities fails due to calculational difficulties for the continuum wavefunctions of very low kinetic energy Auger electrons.
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