Investigation of multicomponent fluoride optical materials in the UV spectral region: I. Single crystals of Ca1−x R xF2+x (R = Sc, Y, La, Yb, Lu) solid solutions

Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca_1?x R _xF_2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region.     

Search for a reliable methodology for PSD determination based on a combined molecular simulation-regularization-experimental approach: The case of PHTS materials

We present here a methodology for searching a robust pore size distribution (PSD) for adsorbent materials. The method is based on a combination of individual adsorption isotherms, obtained from Grand Canonical Monte Carlo simulations, a regularization procedure to invert the adsorption integral equation (Tikhonov regularization solved by singular value decomposition), and the needed experimental adsorption isotherm. The selection of several parameters from the available choices to start the procedure are discussed here: the size of the kernel (number of individual pores and number of experimental adsorption points to be included), the fulfillment of the Discrete Picard condition, and the L-curve criteria, all leading to find a reliable and robust PSD. The procedure is applied to plugged hexagonal templated silicas (PHTS), synthesized, and characterized in our laboratory.     

An Algebraic Method for the Exact Solution of the Partition Function of the Canonical Ensemble in Nuclear Multifragmentation

We propose a unified method for deducing recursive relations for the canonical partition function of a system of noninteracting particles with charge conservation if the particles follow the Bose–Einstein, Fermi–Dirac, or Maxwell–Boltzmann statistics or parastatistics. For all these types of statistics, we find recursive relations for the partition function of a new statistical model of nuclear multifragmentation with electric charge and baryon number conservation, accounting for the internal degrees of freedom of the nuclear fragments.     

K X-ray production cross sections for 40-180 keV protons

Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies ranging from 40 to 180 keV. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polariton gap solitary waves in semiconductor microcavities

We study nonlinear dynamics of optical pulse propagation in the spectral region inside the polariton gap. It is shown that the Kerr nonlinearity can lead to formation of solitary waves in this region of frequencies.     

Dynamics and spectra of excited states of water-micellar suspensions of single-walled carbon nanotubes

The dynamics of the photoinduced differential absorption and excited-state bleaching spectra of single-walled carbon nanotubes suspended in a micellar solution were studied in the spectral range from 40 to 1000 nm within a time interval from 70 fs to 150 ps under excitation by 50-fs pulses with photon energies 2 and 4 eV. The bleaching and absorption bands were observed in the spectra; the positions of the bleaching peaks were independent of the photon energy of the exciting femtosecond pulse in the range 2–4 eV. It was established that, for delay times shorter than 1 ps, the shape of the differential spectrum of excited nanotubes coincided with the shape of the second derivative of the absorption spectrum of unexcited nanotubes in the frequency range of exciting pulse above 18000 cm^?1 (the range of absorption bands of metallic nanotubes). In the frequency range below 16000 cm^?1 (the range of absorption peaks of semiconducting nanotubes), the bleaching peaks in the differential spectrum of excited nanotubes undergo a high-frequency shift of 200–300 cm^?1 with respect to the second-derivative spectrum of unexcited nanotubes. The excited-state relaxation rate constants were measured. They are well approximated by the exponential dependences and depend on the probe-pulse wavelength. An assumption was made about the nature of the observed spectra of excited nanotubes and about the excitation relaxation.