Biomedical subjects

Richard Taïeb

Publications and source records attributed to Richard Taïeb.

3 recordsLinked to original sources

PubMed2005

N-K near-edge x-ray-absorption fine structures of acetonitrile in gas phase.

The dynamic processes of N(1s) core-hole excitation in gas-phase CH3CN molecule have been studied at both Hartree-Fock and hybrid density-functional theory levels. The vibrational structure is analyzed for fully optimized core-excited states. Frank-Condon factors are obtained using the linear coupling model for various potential surfaces. It is found that the vibrational profile of the N-K absorption can be largely described by a summation of two vibrational progressions: a structure-rich profile of nu(CN) stretching mode and a large envelope of congestioned vibrational levels related to the strong (-C-CN) terminal bending bond. Excellent agreement between theoretical and experimental spectra is obtained.

Journal Article↗

PubMed2003

Strong field atomic ionization: origin of high-energy structures in photoelectron spectra.

Two distinct interpretations have been proposed to account for conspicuous enhancements of the ionization peaks in the high energy part of above-threshold ionization spectra. One of them ascribes the enhancement to a multiphoton resonance involving an excited state, while other analysis performed for zero-range model potential link it to "channel closings, " i.e., to the change in the number of photons needed to ionize the atom when the laser intensity increases. We report the results of model calculations that confirm the existence of a resonant process in atoms and shed light on why short-range potential models can mimic the experimental observations.

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PubMed2002

Direct and indirect pathways in strong field atomic ionization dynamics.

With the help of a suitably chosen momentum-space analysis, we study some of the basic mechanisms governing the physics of the processes occurring when atoms are submitted to intense infrared laser pulses, with peak intensities 10(14) W cm(-2)</=I(max)</=10(15) W cm(-2). This intensity range is especially interesting because two highly nonlinear atomic processes, namely, above threshold ionization and high-order harmonic generation, take place with significant probabilities. Several issues regarding the dynamics of these processes are resolved, with special attention devoted to the mechanism leading to the ejection of the photoelectrons in this intensity range.

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