| 1. |
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| 2. |
- Felicissimo, V.C., et al.
(författare)
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Proton transfer mediated by the vibronic coupling in oxygen core ionized states of glyoxalmonoxime studied by infrared-X-ray pump-probe spectroscopy.
- 2006
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 110:47, s. 12805-12813
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Tidskriftsartikel (refereegranskat)abstract
- The theory of IR-X-ray pump-probe spectroscopy beyond the Born-Oppenheimer approximation is developed and applied to the study of the dynamics of intramolecular proton transfer in glyoxalmonoxime leading to the formation of the tautomer 2-nitrosoethenol. Due to the IR pump pulses the molecule gains sufficient energy to promote a proton to a weakly bound well. A femtosecond X-ray pulse snapshots the wave packet route and, hence, the dynamics of the proton transfer. The glyoxalmonoxime molecule contains two chemically nonequivalent oxygen atoms that possess distinct roles in the hydrogen bond, a hydrogen donor and an acceptor. Core ionizations of these form two intersecting core-ionized states, the vibronic coupling between which along the OH stretching mode partially delocalizes the core hole, resulting in a hopping of the core hole from one site to another. This, in turn, affects the dynamics of the proton transfer in the core-ionized state. The quantum dynamical simulations of X-ray photoelectron spectra of glyoxalmonoxime driven by strong IR pulses demonstrate the general applicability of the technique for studies of intramolecular proton transfer in systems with vibronic coupling.
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| 3. |
- Sałek, P., et al.
(författare)
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Resonant X-ray Raman scattering involving avoided crossings in the final-state potential-energy curves
- 2000
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 62:6, s. 62501-62506
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Tidskriftsartikel (refereegranskat)abstract
- The effect of avoided crossings on the spectral profiles of resonant X-ray Raman scattering was investigated. The theory was also applied to nitrogen molecule in the core-excited level to analyze the electron decay process. The dependence of internuclear distance on electron transition amplitude was considered important with respect to the breakdown process of the transition. The correlation between the nuclear and electronic degrees of freedom was also reported.
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| 4. |
- AGREN, H, et al.
(författare)
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SYMMETRY SELECTIVE RESONANT INELASTIC X-RAY-SCATTERING
- 1995
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Ingår i: PHYSICA B. - : ELSEVIER SCIENCE BV. - 0921-4526. ; 209:1-4, s. 105-107
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We use two species with high point group symmetry, fullerene and benzene, to discuss important features of symmetry selective resonant inelastic X-ray scattering spectroscopy.
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| 5. |
- Bjorneholm, O, et al.
(författare)
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Femtosecond dissociation of core-excited HCl monitored by frequency detuning
- 1997
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Ingår i: PHYSICAL REVIEW LETTERS. - : AMER INST PHYSICS. - 0031-9007. ; 79:17, s. 3150-3153
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Core excitation of gaseous HCl to the dissociative sigma* state leads to a deexcitation spectrum with two qualitatively different contributions-a broad molecular background and narrow atomic lines. The experiment demonstrates that the ratio of integrated
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| 6. |
- C. Couto, Rafael, 1987-, et al.
(författare)
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Selective gating to vibrational modes through resonant X-ray scattering
- 2017
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Ingår i: Nature Communications. - : Macmillan Publishers Ltd.. - 2041-1723. ; 8, s. 14165-1-14165-7
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.
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| 7. |
- Cesar, A, et al.
(författare)
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Resonant x-ray scattering beyond the Born-Oppenheimer approximation: Symmetry breaking in the oxygen resonant x-ray emission spectrum of carbon dioxide
- 1997
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Ingår i: Journal of Chemical Physics. - 0021-9606. ; 106:9, s. 3439-3456
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Tidskriftsartikel (refereegranskat)abstract
- Although resonant x-ray scattering of molecules fulfills strict electronic symmetry selection rules, as now firmly proven by. spectra of diatomic molecules, the accumulated body of data for polyatomic molecules indicates that an apparent breaking of these rules represents the common situation rather than the exception. The CO2 molecule provides a good example of symmetry breaking, with the. oxygen x-ray emission spectra showing strong intensity for transitions that are forbidden by the parity selection rule. We present time-independent and time-dependent theories for frequency-dependent resonant x-ray scattering beyond, the Born-Oppenheimer approximation in order to explore under what circumstances one can anticipate symmetry breaking in the spectra of polyatomic molecules. The theory starts out from the Kramers-Heisenberg dispersion relation and is generalized for vibrational degrees of freedom and for nonadiabatic coupling of the electronic (vibronic) states, including the frequency dependency of, the scattering cross section. Different Limiting cases and few-level models are considered. The symmetry breaking is proven to be the result of pseudo-Jahn-Teller-Like vibronic coupling between near-degenerate core-excited states. Thus vibromic interaction over the antisymmetric vibrational mode between the ''bright'' 1 sigma(g)(-1)2 pi(u)(-1) and ''dark'' 1 sigma(u)(-1)2 pi(u)(-1) intermediate states of CO2 allows transitions otherwise forbidden. The measurements and theory demonstrate that the symmetry-selective character of the resonant x-ray emission is strongly frequency dependent. The strong intensity of ''dipole-forbidden'' transitions in the pi* oxygen K spectrum at resonance is reduced monotonically with the detuning of the excitation energy from resonance, and the spectra become ''symmetry purified.'' Simulations with full vibronic coupling predict this feature of the x-ray scattering experiment and a few-level model explains the energy dependence of the symmetry selection and the symmetry purification at large detuning energies in the limit of narrowband photon excitation.
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| 8. |
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| 9. |
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| 10. |
- Couto, Rafael C., et al.
(författare)
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Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12-14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of "dark" with "bright" final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past.
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