Coherent acoustic vibration of metal nanoshells

Using time-resolved pump-probe spectroscopy we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger and the period is longer than in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.Comment: 5 pages, 3 figure

Exceptionally Slow Rise in Differential Reflectivity Spectra of Excitons in GaN: Effect of Excitation-induced Dephasing

Femtosecond pump-probe (PP) differential reflectivity spectroscopy (DRS) and four-wave mixing (FWM) experiments were performed simultaneously to study the initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats between the A-B excitons were found \textit{only for positive time delay} in both PP and FWM experiments. The rise time at negative time delay for the differential reflection spectra was much slower than the FWM signal or PP differential transmission spectroscopy (DTS) at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS results from excitation induced dephasing (EID), that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.Comment: 8 figure

Estimation du Modele de Croissance Neoclassique et Test de ses Proprietes Cycliques sur Donnees Francaises.

cycles economiques ; croissance economique

Hot Carriers in Semiconductors

ultrafast, GaAs, hole, ..................................................................................................................................... ............ ............ ............. ......

The R.B.C. Model Through Statistical Inference an Application on French Data.

statistics ; mathematics ; cycles economiques

Femtosecond investigation of the non-instantaneous third-order nonlinear suceptibility in liquids and glasses

The symmetry of the noninstantaneous Kerr susceptibility is investigated in different liquids and glasses using a time-resolved two-beam energy transfer technique with pulses in the 100–15 fs range. The pulse duration dependence of the ratio of the isotropic to anisotropic tensor elements is demonstrated in liquid CS2 and in silica, showing that the elementary mechanisms mediating the observed optical beam energy transfers are modified for short pulses. This effect is ascribed to alteration of the nuclear contribution and increasing influence of the electronic one

La methode des moments generalisees et ses extensions , theory et applications en macroeconomie.

THEORIE ECONOMIQUE;MACROECONOMIE

Measurement of non-instantaneous contribution to the chi((3)) in different liquids using femtosecond chirped pulses

no abstrac