Oscillatory Size-Dependence of the Surface Plasmon Linewidth in Metallic Nanoparticles

We study the linewidth of the surface plasmon resonance in the optical absorption spectrum of metallic nanoparticles, when the decay into electron-hole pairs is the dominant channel. Within a semiclassical approach, we find that the electron-hole density-density correlation oscillates as a function of the size of the particles, leading to oscillations of the linewidth. This result is confirmed numerically for alkali and noble metal particles. While the linewidth can increase strongly, the oscillations persist when the particles are embedded in a matrix.Comment: RevTeX4, 5 pages, 2 figures, final versio

Thermodynamic description of the Pb-O system

The phase relations and thermodynamic properties of the Pb-O system are reviewed and assessed. The transformation temperature between PbO and Pb3O4 was also experimentally reinvestigated. A model description of the Pb-O system is then proposed and thermodynamic parameters are optimized. The values calculated from the resulting consistent set of Gibbs energy functions are compared with experimental data and discussed

Collective Dipole Oscillations in Atomic Nuclei and Small Metal Particles

(The systematics of photon absorption cross sections in nuclei and small metal particles are examined as a function of the number of constituent fermions $A$. It is pointed out that the shell-structure-linked oscillations in the full width at half maximum (FWHM) of the photoneutron cross section in nuclei, earlier recognized for $A > 63$, in fact persist down to the lightest nuclei. Averaging over the oscillations or focusing on the lower envelope of the oscillating curve (magic nuclei), the FWHM is seen to generally decrease with increasing $A$, consistent with $A^{-1/3}$, a dependence which was earlier known to hold in metal particle systems. If the FWHMs are scaled by the respective Fermi energies and the inverse radii by the Fermi wave vectors, the two data sets become comparable in magnitude. A schematic theoretical description of the systematics is presented.)Comment: 21 pages, 2 figs. (not included), TIFR/TH/92-4

Photochemical incorporation of silver quantum dots in monodisperse silica colloids for photonic crystal applications

We developed a novel method to fabricate nanocomposite monodisperse SiO2 spheres (∼ 100 nm) containing homogeneously dispersed Ag quantum dots (2∼5 nm). The inclusion morphology is controlled through the timing of the photochemical reduction of silver ions during hydrolysis of tetraethoxysilane in a microemulsion. Depending on the timing, Ag quantum dots can be directed to different annuli within the SiO2 spheres, as well as onto the SiO2 sphere surfaces. The embedded Ag quantum dots show a plasmon resonance absorption band at 438 nm. These Ag@SiO2 particles have significant surface charge and readily self-assemble into crystalline colloidal array (CCA) photonic crystals which Bragg-diffract light in the visible region. The magnitude of the plasmon resonance absorption depends on the CCA Bragg diffraction condition. The negative dielectric constant of the silver nanoparticles may be decreasing the silica-silver nanodot composite refractive index below that of the water medium. We may be observing an analogue of the Borrmann effect previously observed in X-ray scattering, where the incident and diffracted electric field standing wave becomes localized in regions of small CCA crystal absorption