Wafa Amir
École Polytechnique
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Publication
Featured researches published by Wafa Amir.
Journal of Chemical Physics | 2002
G. Gallot; S. Bratos; S. Pommeret; Noëlle Lascoux; J-Cl. Leicknam; M. Koziński; Wafa Amir; G.M. Gale
A new theory is proposed to describe spectral effects of the coupling between molecular rotations and OH⋯O motions in liquid water. The correlation function approach is employed together with a special type of development in which the coupling energy of these two motions is the expansion parameter. The isotropy of the liquid medium plays an essential role in this study. Based on this theory, a new infrared pump–probe experiment is described permitting a visualization of molecular rotations at subpicosecond time scales. Full curves relating the mean squared rotational angle and time, and not only the rotational relaxation time, are measured by this experiment. However, very short times where the incident pulses overlap must be avoided in this analysis. The lifetime of OH⋯O bonds in water is rotation–limited.
Journal of Chemical Physics | 2007
Wafa Amir; Guilhem Gallot; F. Hache; S. Bratos; Jean-Claude Leicknam; Rodolphe Vuilleumier
Experimental observation and time relaxation measurement of the hydrated proton Eigen form [H(3)O(+)(H(2)O)(3)] are presented here. Vibrational time-resolved spectroscopy is used with an original method of investigating the proton excess in water. The anharmonicity of the time-resolved spectra is characteristic of the Eigen-type proton geometry. Proton relaxation occurs in less than 200 fs. A calculation of the potential energy confirms the experimental result and the Eigen cation lifetime is in good agreement with previous molecular dynamics simulations.
Journal of Chemical Physics | 2004
Wafa Amir; Guilhem Gallot; François Hache
We developed an experimental approach to study pure liquid water in the infrared and avoid thermal effects. This technique is based on libration induced stretching excitation of water molecules. A direct correspondence between frequencies within the libration and OH stretching bands is demonstrated. Energy diffusion is studied in pure liquid water by measuring wave packet dynamics of OH stretching vibrator with infrared femtosecond spectroscopy. Wave packet dynamics reveals ultrafast energy dynamics and reflects 130 fs intermolecular energy transfer between water vibrators. Energy diffusion is almost two orders of magnitude faster than self diffusion in water.
Procedia Engineering | 2004
Wafa Amir; Giovanni Gallot; F. Hache
Procedia Engineering | 2004
Wafa Amir; Guilhem Gallot; F. Hache
Journal De Physique Iv | 2004
Wafa Amir; Guilhem Gallot; F. Hache
The Thirteenth International Conference on Ultrafast Phenomena (2002), paper TuE28 | 2002
S. Pommeret; S. Bratos; J.-Cl. Leicknam; G. Gallot; Noëlle Lascoux; G.M. Gale; Wafa Amir
Nonlinear Optics: Materials, Fundamentals and Applications (2002), paper ThC7 | 2002
Guilhem Gallot; Noëlle Lascoux; Wafa Amir; G.M. Gale; S. Bratos; J-Cl. Leicknam; S. Pommeret
Journal De Physique Iv | 2002
Wafa Amir; N. Lascoux; G. Gallot; G.M. Gale; S. Pommeret; J.-Ci. Leicknam; S. Bratos
Bulletin de la Societe Francaise de Physique | 2002
Guilhem Gallot; S. Bratos; G.M. Gale; Noëlle Lascoux; J.-Cl. Leicknam; S. Pommeret; Wafa Amir