Scattering of ultrashort electromagnetic pulses on the dense strongly coupled plasma is under consideration in the frame of hard ion sphere model. The electron distribution inside the ion sphere is obtained from self-consistent solution of the Shrodinger equation for bound electrons and the Poisson equation for free electrons. The electron density distribution is determined by plasma electron temperatures. The ion density of Al plasmas under consideration is of the order of 10 20 -10 22 cm −3 , the electron temperature changes between 54 and 816 eV. Dynamical polarizability of the hard sphere determining the scattering cross sections is calculated using the modified local plasma frequency approximation. The spectrum of scattering cross section has maxima in the vicinity of the mean plasma frequency. Dependencies of scattering probability on carrier frequency and pulse duration are analysed in detail. The transition of the total scattering probabilities from nonlinear time dependence at small times to standard linear ones with the increase of pulse duration is demonstrated. KEYWORDSdynamical polarizability, ion sphere, local plasma frequency, scattering cross section, scattering probability, ultrashort laser pulse INTRODUCTIONModern progress in generation of ultrashort laser pulses (USPs) [1,2] requires the development of adequate methods for the description of the interaction of such pulses with different targets. The conventional approach based on the concepts of probability per unit time and intensity of the radiation used for long quasi-monochromatic pulses appears to be insufficient in the case of USP. [3] In fact, probability per unit time arises in quantum mechanical consideration as a limit when the pulse duration tends to infinity. [4] In such an approach, it is assumed that the timescale of the target internal motion is much smaller than the pulse duration. The last assumption becomes incorrect for sufficiently short pulses. Then, one should describe the photoprocess in terms of total probability during the entire time of the pulse action and electric field strength in the pulse instead of probability per unit time and pulse intensity. [5] The conditional consideration of radiation scattering in ideal plasmas is based on the account of free electron density fluctuations and fluctuations of screened electron density near ions. These two contributions to scattering probabilities are the sum of Thomson scattering on free electrons and transition scattering on the Debye screening sphere. [6] In contrast with ideal plasmas, the electron structure in strongly coupled plasmas is determined by strong ion-ion correlations resulting in the formation of a plasma structure in the form of isolated hard ion spheres (the so called "ion sphere model," see ref.[7]). Ion spheres are separated by ion's sphere radii of the order of interion distances and contain both bound and free electrons that are distributed strongly nonuniformly. The last makes it actual to look for light scattering on such structures.

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles.