| 1. |
- Jahnke, T., et al.
(författare)
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Inner-Shell-Ionization-Induced Femtosecond Structural Dynamics of Water Molecules Imaged at an X-Ray Free-Electron Laser
- 2021
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Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 11:4
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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.
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| 2. |
- Li, S., et al.
(författare)
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Manifestation of postcollision interaction in Krypton LMN Auger spectra following K-shell photoionization
- 2022
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 106:2
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Tidskriftsartikel (refereegranskat)abstract
- We report on an experimental and theoretical study of postcollision interaction (PCI) effects on L-2 - M4,5N2,3 Auger electrons measured above the Kr K-edge in which L-2 vacancies are primarily generated by KL2 x-ray emission. Such cascade processes, in which a deep inner-shell vacancy decays first by x-ray emission followed by Auger electron emission, is a strong decay mode in heavy atoms. The L-2 - M4,5N2,3 Auger electron peak is observed to become increasingly asymmetric with a shifting peak maximum as the absorbed x-ray energy approaches the K-shell ionization threshold. This is attributed to PCI energy exchanges of the Auger electron with the 1s photoelectron. To model the PCI effects, we have applied a semiclassical approach modified to account for the combined lifetimes of the K and L-2 hole states. In addition, our analysis treats several closely spaced Auger transitions with final ionic states having different terms and angular momenta.
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| 3. |
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| 4. |
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| 5. |
- Baev, A., et al.
(författare)
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Geometrical information on core-excited states obtained from interference quenching of vibrational states in resonant x-ray photoemission
- 2003
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 67:2
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Tidskriftsartikel (refereegranskat)abstract
- An interference quenching of the m=1 final state vibrational line in the resonant Auger decay of N 1s-->pi(*) core-excited N-2 is observed and analyzed. The intensity ratio between the m=1 and m=0 vibrational levels of the X (2)Sigma(g)(+) final state shows a surprising nonmonotonic variation as a function of frequency detuning, going through a minimum with a complete suppression of m=1. We have developed a simple model which indicates a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance of the core-excited state. This implies the possibility of determining the equilibrium bond distances for core-excited states to a high degree of accuracy. Simultaneously with the simple model we present a strict theory of the studied effect. This strict theory allows us to explore the accuracy of determining the bond length of the core-excited state from resonant Auger spectra. We obtain a weak influence of the core-hole lifetime on the determined bond length, whereas the number of intermediate vibrational states accounted for in the numerical simulations seems to be quite important.
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| 6. |
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| 7. |
- Feifel, R., et al.
(författare)
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"Hidden" vibrations in CO : Reinvestigation of resonant Auger decay for the C 1s → π* excitation
- 2002
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 65:5 A, s. 527011-527018
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Tidskriftsartikel (refereegranskat)abstract
- The higher vibrational levels of the C 1s→π* excitation in carbon monooxide (CO) were investigated by using resonant Auger electron spectroscopy. The absorption profile of the CO was recorded in the partial electron yield mode. The results showed that the vibrational states were not seen in a total yield absorption spectrum whereas they were shown to be discernable in a partial electron yield spectrum.
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| 8. |
- Feifel, R., et al.
(författare)
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Interference quenching of nu('')=1 vibrational line in resonant photoemission of N-2 : A possibility to obtain geometrical information on the core-excited state
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 89:10
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Tidskriftsartikel (refereegranskat)abstract
- An interference quenching of the nu=1 vibrational line in the resonant Auger decay of N 1s-->pi(*) core-excited N-2 is observed and analyzed. The intensity ratio between the nu=1 and nu=0 vibrational levels of the X(2)Sigma(g)(+) final state shows a surprising nonmonotonous variation as a function of frequency detuning, going through a minimum with a complete suppression of nu=1. We have developed a simple model which shows a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance R-c(0) of the core-excited state. A new way is thus established of determining the equilibrium bond distance for the core-excited state with a precision deltaR(c)(0)<10(-3) Angstrom.
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| 9. |
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| 10. |
- Hennies, F., et al.
(författare)
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Dynamic interpretation of resonant x-ray Raman scattering : ethylene and benzene
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:3, s. 032505-
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Tidskriftsartikel (refereegranskat)abstract
- We present a dynamic interpretation of resonant x-ray Raman scattering where vibrationally selective excitation into molecular resonances has been employed in comparison with excitation into higher lying continuum states for condensed ethylene and benzene as molecular model systems. In order to describe the purely vibrational spectral loss features and coupled electronic and vibrational losses the one-step theory for resonant soft x-ray scattering is applied, taking multiple vibrational modes and vibronic coupling into account. The scattering profile is found to be strongly excitation energy dependent and to reflect the intermediate states dynamics of the scattering process. In particular, the purely vibrational loss features allow one to map the electronic ground state potential energy surface in light of the excited state dynamics. Our study of ethylene and benzene underlines the necessity of an explicit description of the coupled electronic and vibrational loss features for the assignment of spectral features observed in resonant x-ray Raman scattering at polyatomic systems, which can be done in both a time independent and a time dependent picture. The possibility to probe ground state vibrational properties opens a perspective to future applications of this photon-in-photon-out spectroscopy.
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