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- Ågren, Hans, et al.
(author)
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Dynamics of Inner Shell Resonant Raman Scattering.
- 1999
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In: Journal of the Japanese Society for Synchrotron Radiation Research. - 0914-9287. ; 12:4, s. 257-267
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Journal article (peer-reviewed)abstract
- Some recent advances in the theory of the resonant Raman process for atoms, molecules and solids involving inner shell electrons are reviewed. Special emphasis is put on the dynamical aspects and on the notion of a duration time for the x-ray Raman process (RXS), which brings about a distinetion of processes with different time scales responsible for the formation of the spectral profile. This notion has been useful for actual predietions of various phenomena associated with RXS such as "symmetry restoration" "vibrational collapse", and "control of dissociation". The temporal theory of RXS is based on the wave packet formalism. The increase of the broad "molecular" parts relative to the atomic, or fragment, decay upon frequency detuning is demonstrated. The atomic-like resonance and molecular parts are proved to show different dispersion relations. Under certain conditions the interference between the molecular and atomic parts produces conspicuous "spectral holes". These conceptual tools are applicable also in the case of solids; there is an analogous restoration of momentum selection rules and a collapse effect upon detuning the frequency. Thus when the duration of the scattering is shortened by a large detuning, the role of electron-phonon coupling of the core excited states is suppresssed. The shortening of the RXS duration in a certain sense leads to a deloealization of the core hole in a solid. We describe also some new features that derive from the Doppler effect on ejected Auger electrons.
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