Ultrafast response of surface electromagnetic waves in an aluminum film perforated with subwavelength hole arrays

The ultrafast dynamics of surface electromagnetic waves photogenerated on aluminum film perforated with subwavelength holes array was studied in the visible spectral range by the technique of transient photomodulation with 100 fs time resolution. We observed a pronounced blueshift of the resonant transmission band that reveals the important role of plasma attenuation in the optical response of nanohole arrays. The blueshift is inconsistent with plasmonic mechanism of extraordinary transmission and points to the crucial role of interference in the formation of transmission bands. The transient photomodulation spectra were successfully modeled within the Boltzmann equation approach for the electron-phonon relaxation dynamics, involving non-equilibrium hot electrons and quasi-equilibrium phonons.Comment: 4 pages, 3 figure

Multifragmentation in Collisions of 4.4gev-Deuterons with Gold Target

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collitions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay timees of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emossion time is found to be less than 40 fm/c.Comment: Accepted for publication in Bulletin of the Russian Academy of Sciences. Physic

Extraordinary electron transmission through a periodic array of quantum dots

We study electron transmission through a periodic array of quantum dots (QD) sandwiched between doped semiconductor leads. When the Fermi wavelength of tunneling electron exceeds the array lattice constant, the off-resonant per QD conductance is enhanced by several orders of magnitude relative to the single-QD conductance. The physical mechanism of the enhancement is delocalization of a small fraction of system eigenstates caused by coherent coupling of QDs via the electron continuum in the leads.Comment: 4 pages, 3 figure

Multifragmentation and nuclear phase transitions (liquid-fog and liquid-gas)

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition. The charge distributions of the intermediate mass fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are analyzed within the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition Tc as a free parameter. The analysis presented here provides strong support for a value of Tc > 15 MeV.Comment: 4 pages, 2 figures, Submittet to Proc. of NN2003 to be published in Nucl. Phys.

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

Vibrational modes of metal nanoshells and bimetallic core-shell nanoparticles

We study theoretically spectrum of radial vibrational modes in composite metal nanostructures such as bimetallic core-shell particles and metal nanoshells with dielectric core in an environment. We calculate frequencies and damping rates of fundamental (breathing) modes for these nanostructures along with those of two higher-order modes. For metal nanoshells, we find that the breathing mode frequency is always lower than the one for solid particles of the same size, while the damping is higher and increases with reduction of the shell thickness. We identify two regimes that can be characterized as weakly damped and overdamped vibrations in the presence of external medium. For bimetalllic particles, we find periodic dependence of frequency and damping rate on the shell thickness with period determined by mode number. For both types of nanostructures, the frequency of higher modes is nearly independent of the environment, while the damping rate shows strong sensitivity to outside medium.Comment: 7 pages, 8 figure