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- Brena, Barbara, et al.
(författare)
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Ultrafast Molecular Dissociation of Water in Ice
- 2004
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Ingår i: Physical Review Letters. - : The American Physical Society. - 1079-7114 .- 0031-9007. ; 93, s. 148302-148305
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Tidskriftsartikel (refereegranskat)abstract
- Using x-ray emission and photoemission spectroscopies to measure the occupied valence levels in a thin crystalline ice film, we resolve the ionization-induced dissociation of water in ice on a femtosecond time scale. Isotope substitution confirms proton transfer during the core-hole lifetime in spite of the nonresonant excitation. Through ab initio molecular dynamics on the core-ionized state, the dissociation and spectrum evolution are followed at femtosecond intervals. The theoretical simulations confirm the experimental analysis and allow for a detailed study of the dissociative reaction path.
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- Cavalleri, M., et al.
(författare)
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Half or full core hole in density functional theory X-ray absorption spectrum calculations of water?
- 2005
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 7:15, s. 2854-2858
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the performance of two different core-hole potentials in the theoretical modeling of XAS of ice, liquid and gas phase water; the use of a full core-hole (FCH) in the calculations, as suggested by Hetenyi et al. [B. Hetenyi, F. De Angelis, P. Giamozzi and R. Car, J. Chem. Phys., 2004, 120(18), 8632], gives poor agreement with experiment in terms of intensity distribution as well as transition energies, while the half core hole (HCH) potential, in the case of water, provides a better compromise between initial and final state effects, leading to good agreement with the experimental data.
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- Cavalleri, M., et al.
(författare)
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X-absorption spectra of water within a plane-wave Car-Parrinello molecular dynamics framework
- 2004
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics. - 0021-9606 .- 1089-7690. ; 121:20, s. 10065-10075
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Tidskriftsartikel (refereegranskat)abstract
- We describe the implementation of a simple technique to simulate core-level spectra within the Car-Parrinello plane-waves molecular dynamics framework. The x-ray absorption (XA) spectra are generated using the transition potential technique with the effect of the core hole included through a specifically developed pseudopotential for the core-excited atom. Despite the lack of 1s core orbitals in the pseudopotential treatment, the required transition moments are accurately calculated without reconstruction of the all-electron orbitals. The method is applied to the oxygen XA spectra of water in its various aggregation states, but it is transferable to any first-row element. The computed spectra are compared favorably with the results from all-electron cluster calculations, as well as with experimental data. The periodicity of the plane-wave technique improves the description of condensed phases. The molecular dynamics simulation enables in principle a proper treatment of thermal effects and dynamical averaging in complex systems.
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