Measurement of 16O5+ Induced L X-Ray Production Cross Sections for Gold

The characteristic Ll, Lα, Lβ and Lγx-rays of Au and energy shifts produced by 20–50MeV 16O5+ beams on a thick Au ilm are measured with a Si (Li) detector. Cross-section ratios of σ(Ll)/σ(Lα), σ(Lβ)/σ(Lα) andσ(Lγ)/σ(Lα) versus O5+ energy show that consistent calculations yield considerably better agreements. Energy shifts Ll, Lα, Lβ and Lγ x-rays of Au target increase with more incidence energy. The main application for these measurements is multi-element trace analysis through particle induced x-ray emission.

Preparation of Hollow Carbon and Silicon Carbide Fibers with Different Cross-Sections by using Electrospun Fibers as Templates

Hollow carbon nanofibers with circular and rectangular opening were prepared by using electrospun silica fibers as templates. Silica fibers were synthesized by electrospinning, and they were coated with a carbon layer formed by thermal decomposition and carbonization of polystyrene under a nitrogen atmosphere. Hollow carbon nanofibers with circular and rectangular openings were then obtained after the silica core was etched by hydrofluoric acid. The carbon nanofibers with different morphologies also could be used as templates to fabricate silicon carbide fibers. The silicon carbide fibers with circular and rectangular openings could be obtained by using hollow carbon nanofibers and carbon belts as templates, respectively.

Resonant mode analysis in toroidal cavities with elliptic cross-sections

Resonant cavity modes in a torus with elliptical cross section are studied by means of a direct variational method. The nonlinear effects of toroidicity and ellipticity on the frequency of the basic mode are analyzed simply and systematically without the restriction of linear theory. It is shown that the toroidicity effect on the m = 0 transverse magnetic mode is less-than-or-equal-to 11%. The frequency of the mode shifts approximately 11-29% when the elongation of the cross section changes from 1 to 2. The effects of toroidicity and ellipticity differ for each resonant mode.

Enhancement of three-photon absorption cross-sections in a novel class of symmetrical charge transfer fluorene-based molecules

The three-photon absorption effect (3PA) of two novel symmetrical charge transfer fluorene-based molecules (abbreviated as BASF and BMOSF) has been determined by using a Q-switched Nd:YAG laser pumped with 38 ps pulses at 1064 nm in DMF. The measured 3PA cross-sections are 84 x 10(-78) and 114 x 10(-78) cm(6) s(2), respectively. The geometries and electronic excitations of these two molecules are systematically studied by PM3 and ZINDO/S methods. The relationships between 3PA cross-sections and intramolecular charge transfer are discussed micromechanically. The experimental and theoretical results have shown that the larger intramolecular charge transfer, which was characterized by the charge density difference between the ground state (SO) and the first excited state (S-I), the greater enhancement of the 3PA cross-sections. (c) 2005 Elsevier B.V. All rights reserved.

Effect of F- ions on emission cross-section and fluorescence lifetime of Yb3+-doped tellurite glasses

The effects of F- ions in Yb3+-doped tellurite glass systems on the emission cross-section and measured fluorescence lifetime are investigated. The results show that both the emission cross-section and the fluorescence lifetime of Yb3+ ions increase from 1.32 to 1.39 pm(2) and from 0.93 to 1.12 ms respectively with the increase of F- ions from 0 to 10 mol% and that such oxyfluoride tellurite glass system is a promising laser host matrix for high power generation. FT-IR spectra were used to analyze the effect of F- ions on the structure of tellurite glasses and the change of OH- groups in this glass system. Analysis demonstrates that the addition of fluoride decreases the symmetry of the structure of tellurite glasses resulting in increasing of the emission cross-section and removes the OH- groups resulting in increasing of the measured fluorescence lifetime of Yb3+ ions. (c) 2005 Elsevier B.V. All rights reserved.

Temperature dependence of the 1.03 mu m stimulated emission cross section of Cr : Yb : YAG crystal

The fluorescence emission spectra of Cr:Yb:YAG crystal are measured and the effective stimulated emission cross section of the crystal are obtained from -80 degrees C to +80 degrees C. A linear temperature dependence between -80 degrees C and +80 degrees C is reported for the 1.03 mu m peak stimulated emission cross section of Cr:Yb:YAG crystal. (c) 2004 Elsevier B.V. All rights reserved.

Temperature dependence of the 1.064-mu m stimulated emission cross-section of Cr : Nd : YAG crystal

The fluorescence emission spectra of Cr:Nd:YAG crystal are measured and the effective stimulated emission cross-section of the crystal is obtained from -80 to +80 degrees C. A linear temperature dependence between -80 and +80 degrees C is reported for the 1.064-mu m peak stimulated emission cross-section of Cr:Nd:YAG crystal. (C) 2005 Elsevier Ltd. All rights reserved.

Single-mode condition for silicon rib waveguides with large cross sections

The single-mode condition for silicon rib waveguides with large cross sections is obtained using a numerical method based on the finite-difference beam propagation method (FD-BPM). An ultrawide computation window is used to contain the wide mode profile near cutoff. Comparison with previous results shows that the formula predicted by the mode-matching technique is in a better agreement with our results. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Nd3+-doped LaF3 nanoparticles with a larger emission cross-section

A series of Nd3+-doped LaF3 nanoparticles with Nd3+ concentrations from 0.5 to 10 mol% were synthesized. The fluorescence intensity and lifetime of the nanoparticles at various Nd3+ doping concentration were investigated. The nanoparticles displayed strongest fluorescence intensity at 3 mol% Nd3+ concentration. Eighty-eight percentage quantum efficiency was obtained when the Nd3+ concentration was 0.5 mol%. Optical properties of nanoparticles were studied according to Judd-Ofelt theory. A larger emission cross-section, sigma(em), for F-4(3/2) -> I-4(11/2) transition of the Nd3+ ion was obtained as 3.21 x 10(-20) cm(2), which was two times of the currently reported value. The larger emission cross-section and strong fluorescence intensity demonstrate that these nanoparticles are promising materials for laser applications. (C) 2010 Published by Elsevier B. V.

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

197Au were irradiated with 47 MeV/u 12C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of 197Au with 12C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich iso...