Nonlinear Refraction and Absorption of Ag 29 Nanoclusters: Evidence for Two-Photon Absorption Saturation

International audienc

Universal scaling of plasmon coupling in metal nanostructures: Checking the validity for higher plasmonic modes using second harmonic generation

The universal scaling of plasmon coupling in metallic nanostructures is now a well-established feature. However, if the interaction between dipolar plasmon modes has been intensively studied, this is not the case of the coupling between higher order ones. Using Mie theory extended to second harmonic generation, we investigate the coupling between quadrupolar plasmon modes in metallic nanoshells. Like in the case of dipolar plasmon modes, a universal scaling behavior is observed in agreement with the plasmon hybridization model

Second harmonic scattering from silver nanocubes

The second harmonic light scattered from silver nanocubes dispersed in an aqueous suspension is investigated. The first hyperpolarizability is determined and corrected for resonance enhancement. It is shown to be similar to that of silver nanospheres with a comparable volume. The polarization-resolved analysis of the scattered harmonic intensity exhibits a surface response strongly modulated by the different multipolar field contributions. As a result, the shape does not play a leading role anymore for nanoparticles with a centrosymmetric shape when retardation must be considered. Comparing the right angle and forward-scattered polarized intensity responses, the unequal balance of the eight nanocube corners' contribution to the total response is revealed despite the high degree of centrosymmetry of the cubic shape. It is then demonstrated with a simple model that the nanocubes' first hyperpolarizability exhibits an octupolar tensorial symmetry. The surface integral equation method calculations are finally provided to investigate further the role of the corners’ and edges’ rounding

Thermal fluctuations of a metal atom on a C₆₀ surface

Fluctuations of a rubidium atom on the surface of a fullerene cage have been observed by measuring the electric susceptibility of isolated RbC60 molecules. The evolution of the susceptibility with the temperature is perfectly reproduced with a very simple statistical model of relaxation. The correlation time for these fluctuations and the activation energy (Ea=0.02 eV) for the motion of the alkali-metal atom on the C60 surface have been determined

Electric dipole moment and charge transfer in alkali-C

We have measured the electric dipole moment of isolated alkali-C60 molecules (with alkali = Li, Na, K, Rb, and Cs) by molecular beam deflection experiments. The dipole increases from 12.4 D for LiC60 to 21.5 D for CsC60. These results are compared to those deduced from an analytical polarizable-ion model. This comparison shows that there is a strong electron transfer from the alkali atom to the C60 cage, which is almost complete for KC60 and RbC60