Diode-pumped Nd:YVO<Subscript>4</Subscript> and Nd:KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> 1.3 μm lasers passively Q-switched with PbS-doped glass

Diode-pumped Nd:YVO₄ and Nd:KGW lasers passively Q-switched with PbS-quantum dot-doped phosphate glass were demonstrated. For the Nd:YVO₄ laser, pulses 110 ns in duration with a 13% Q-switching efficiency were obtained. The absorption recovery time of the PbS-doped glass was measured to be 27±4 ps. Some recommendations for more efficient use of PbS-doped glasses for Q-switching of diode-pumped lasers are suggested on the basis of our analysis. Received: 29 July 2002 / Revised version: 18 September 2002 / Published online: 12 February 2003 RID="*" ID="*"Corresponding author. Fax: +375-17/232-6286, E-mail: savitski@eudoramail.com     

Non-perturbative calculations for the effective potential of the PT symmetric and non-Hermitian (-gφ<Superscript>4</Superscript>) field theoretical model

We investigate the effective potential of the PT symmetric (-gφ⁴) field theory, perturbatively as well as non-perturbatively. For the perturbative calculations, we first use normal ordering to obtain the first order effective potential, from which the predicted vacuum condensate vanishes exponentially as G→0⁺, in agreement with previous calculations. For the higher orders, we employ the invariance of the bare parameters under the change of the mass scale t to fix the transformed form totally equivalent to the original theory. The form so obtained up to G³ is new and shows that all the 1PI amplitudes are perturbative for both the and the region. For the intermediate region, we modified the fractal self-similar resummation method to have a unique resummation formula for all G values. This unique formula is necessary, because the effective potential is the generating functional for all the one-particle irreducible (1PI) amplitudes that can be obtained via ∂ⁿE/∂bⁿ, and thus we can obtain an analytic calculation of the 1PI amplitudes. Again, the resummed form of the effective potential is new and interpolates the effective potential between the perturbative regions. Moreover, the resummed effective potential agrees in spirit to a previous calculation concerning bound states. PACS 11.10.Kk; 02.30.Mv; 11.10.Lm; 11.30.Er; 11.30.Qc; 11.15.Tk     

<Emphasis Type="Italic">D</Emphasis>-Wave Resonances in Three-Body System Ps<Superscript>−</Superscript> with Pure Coulomb and Screened Coulomb (Yukawa) Potentials

We have investigated the doubly excited ¹ D ^e resonance states of Ps⁻ interacting with pure Coulomb and screened Coulomb (Yukawa) potentials employing highly correlated wavefunctions. For pure Coulomb interaction, in the framework of stabilization method and complex coordinate rotation method we have obtained two resonances below the n = 2 threshold of the Ps atom. For screened Coulomb interaction, we employ the stabilization method to extract resonance parameters. Resonance energies and widths for the ¹ D ^e resonance states of Ps⁻ for different screening parameter ranging from infinity (pure Coulomb case) to a small value are also reported.     

Fine structure of the strength function for the β<Superscript>+</Superscript>/EC decay of the <Superscript>160<Emphasis Type="Italic">m</Emphasis></Superscript>Ho (5.02 h) isomer

The strength function for the β⁺/EC decay of the deformed nucleus of the ^160m Ho (5.02 h) isomer is obtained from the experimental data, The fine structure of the strength function S _β(E) is analyzed. It has a pronounced resonance structure for Gamow-Teller transitions and is found to exhibit a resonance structure for first-forbidden transitions. It is shown that for some excitation energies of the 160Dy daughter nucleus the probability of first-forbidden β⁺/EC transitions in the decay of the ^160m Ho isomer is comparable with the probability of Gamow-Teller β⁺/EC transitions.     

Dipoles and band alignment for benzene/Au(111) and C<Subscript>60</Subscript>/Au(111) interfaces

A local orbital DFT-approach combined with a “scissor”-operator is used to obtain the Charge Neutrality Level and the screening parameter in the benzene/Au(111) and C₆₀/Au(111) interfaces. The “pillow” dipole and interface Fermi level are also calculated. The total dipole induced across the interface is compared with the experimental evidences: while the agreement for C₆₀/Au(111) is excellent, for benzene/Au(111), some discrepancies appear that are discussed in the light of other models.     

Perovskite-type (Ba<Subscript>0.15</Subscript>Sr<Subscript>0.85</Subscript>)(B<Subscript>0.15</Subscript>Co<Subscript>0.85</Subscript>)O<Subscript>3 − δ</Subscript> (B = Ti,Nb) oxides: structural stability,oxygen nonstoichiometry,and oxygen sorption/desorption properties

The perovskite-type Ba- and Ti/Nb-doped (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) oxides were synthesized successfully by the solid-state reaction method. Crystal structure, elemental compositions, and oxygen nonstoichiometry of the as-synthesized (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) oxides were investigated by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), inductively coupled plasma (ICP)-atomic emission spectrometry, thermogravimetry (TG), and iodometric titration. XRD results demonstrate that the as-obtained (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) oxides possess purely cubic perovskite-type structures. The temperature-swing oxygen sorption/desorption properties of the as-synthesized (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) perovskite-type oxides were studied by the dynamic TG. Results show that the structural stability of the co-doped (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) oxides is improved greatly, and the high oxygen sorption capacity for the perovskite-type (Ba_0.15Sr_0.85)(B_0.15Co_0.85)O_3 ? δ (B = Ti, Nb) oxides is also obtained between 300 and 950 °C in air.     

Preliminary results of the cross-section measurement of e<Superscript>+</Superscript>e<Superscript>−</Superscript> → φ(1020)η process with the CMD-3 detector at VEPP-2000 collider

We report preliminary results on the cross section of the process e⁺e^? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb^?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy.     

On the classes H<Subscript><Emphasis Type="Italic">p</Emphasis></Subscript><Superscript>ω</Superscript> and Lip (α, <Emphasis Type="Italic">p</Emphasis>) for trigonometric series with monotone coefficients

The paper is devoted to the study of a relationship between the behavior of the coefficients of trigonometric series of many variables and the smoothness of the sums of these series in the spaces L _p .     

White Light Emitting MZr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript>:Dy<Superscript>3+</Superscript> (M = Ca,Sr, Ba) Phosphors for WLEDs

A series of MZr₄(PO₄)₆:Dy³⁺ (M = Ca, Sr, Ba) phosphors were prepared by the solid state diffusion method. Confirmation of the phase formation and morphological studies were performed by X-ray powder diffraction (XRD) measurements and scanning electron microscopy, respectively. Photoluminescence (PL) properties of these phosphors were thoroughly analyzed and the characteristic emissions of Dy³⁺ ions were found to arise from them at an excitation wavelength of 351 nm. The PL emission spectra of the three phosphors were analyzed and compared. The CIE chromaticity coordinates assured that the phosphors produced cool white-light emission and hence, they are potential candidates for UV excited white-LEDs (WLEDs).

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Graphical Abstract ?

     

Correlation of structure parameters of absorber layer with efficiency of Cu(In,Ga)Se<Subscript>2</Subscript> solar cell

Polycrystalline Cu(In, Ga)Se₂ with Ga-content x=Ga/(In+Ga) ranging from 0.0 (CuInSe₂) to 1.0 (CuGaSe₂) in heterojunction thin film solar cells were grown by multi-source evaporation. Solar cells with a highest efficiency of η=15.3% need a composition of x≈0.2. At this composition, the c/a ratio of the lattice constants for the tetragonal lattice equals c/a=2, indicating ideal tetragonality. These results suggest that low electronic defect densities occur at x≈0.2, due to the smallest possible crystallographic distortion of the tetragonal lattice at this composition. Cells with high efficiencies require grain sizes above 145 nm and a high preferred orientation (P₂₀₄/P₂₂₀ pole density ratio) for the grains.     

Geometric Model for Complex Non-Kähler Manifolds with <Emphasis Type="Italic">SU</Emphasis> (3) Structure

For a given complex n-fold M we present an explicit construction of all complex (n+1)-folds which are principal holomorphic T²-fibrations over M. For physical applications we consider the case of M being a Calabi-Yau 2-fold. We show that for such M, there is a subclass of the 3-folds that we construct, which has natural families of non-Kähler SU(3)-structures satisfying the conditions for supersymmetry in the heterotic string theory compactified on the 3-folds. We present examples in the aforementioned subclass with M being a K3-surface and a 4-torus.     

Size effect in spin-crossover systems investigated by FORC measurements,for surfacted [Fe(NH<Subscript>2</Subscript>-trz)<Subscript>3</Subscript>](Br)<Subscript>2</Subscript>·3H<Subscript>2</Subscript>O nanoparticles: reversible contributions and critical size

We investigated the thermal transition of coated nano-particles of the title compound, on a set of samples of average diameter ⟨d⟩ ~ 30, 50, 70, 110 nm, with rather broad size distributions. As expected, the width of the major hysteresis loop was an increasing function of ⟨d⟩. We recorded first-order reversal curves (FORC), the initial parts of which displayed a finite slope, revealing the presence of reversible contributions expected from particles smaller than the critical size d _C associated with the collapse of the hysteresis loop. Kinetic effects were also evidenced thanks to isothermal stages. Reversibility of the FORC curves at the vicinity of the reversal temperature was controlled. Thanks to the reversibility property we could determine the reversible contributions to the total response of all samples and derive the corresponding d _C values. Consistent results were obtained by accounting for an anhysteretic contribution from the large particles, leading to an accurate determination d _C  ~ 45−50 nm, much better than the width of the size distributions.     

Poly (ethylene oxide) (PEO)-based,sodium ion-conducting‚ solid polymer electrolyte films,dispersed with Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filler,for applications in sodium ion cells

The studies on solid polymer electrolyte (SPE) films with high ionic conductivity suitable for the realization of all solid-state Na-ion cells? form the focal theme of the work presented in this paper. The SPE films are obtained by the solution casting technique using the blend solution of poly (ethylene oxide) (PEO) with ethylene carbonate (EC) and propylene carbonate (PC) and complexed with sodium nitrate. Structural and thermal studies of SPE films are done by XRD, FTIR spectroscopy, and TGA techniques. Surface morphology of the films is studied using the FESEM. The ionic conductivity of SPE films is determined from the electrochemical impedance spectroscopy studies. For the SPE film with 16 wt% of NaNO₃ used for reacting with the polymer blend of PEO with EC and PC, the ionic conductivity obtained is around 1.08 × 10^?5 S cm^?1. Addition of the Al₂O₃ as the filler material is found to enhance the ionic conductivity of the SPE films. The studies on the Al₂O₃ modified SPE film show an ionic conductivity of 1.86 × 10^–4 S cm^?1, which is one order higher than that of the SPE films without the filler content. For the SPE film dispersed with 8 wt% of Al₂O₃, the total ion transport number observed is around 0.9895, which is quite impressive from the perspective of the applications in electrochemical energy storage devices. From the cyclic voltammetry studies, a wide electrochemical stability window up to 4 V is observed, which further emphasizes the commendable electrochemical behavior of these SPE films.     

TEM,XRD and AFM study of poly(<Emphasis Type="Italic">o</Emphasis>-ethoxyaniline) films: new evidence for the formation of conducting islands

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH=3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasi-one dimensional variable range hopping (VRH) mechanism.     

Time Resolved Fluorescence and Energy Transfer Analysis of Nd<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript>–Er<Superscript>3+</Superscript> Triply-Doped Ba–Al-Metaphosphate Glasses for an Eye Safe Emission (1.54 μm)

This paper reports on the preparation and systematic analysis of energy transfer mechanisms in Nd³⁺–Yb³⁺–Er³⁺ co-doped new series of barium-alumino-metaphosphate glasses. The time resolved fluorescence of Nd³⁺ in triply doped Ba–Al-metaphosphate glasses have revealed that, Yb³⁺ ions could function as quite efficient bridge for an energy transfer between Nd³⁺ and Er³⁺ ions. As a result, a fourfold emission enhancement at 1.54 μm of Er³⁺ ions has been achieved through an excitation of ⁴F_5/2 level of Nd³⁺ at 806 nm for the glass having 3 mol% Yb³⁺ with an energy transfer efficiency reaching up to 94%. Decay of donor (Nd³⁺) ion fluorescence has been analyzed based on theoretical models such as direct energy transfer model (Inokuti–Hirayama) and migration assisted energy transfer models (Burshtein’s hopping and Yokota–Tanimoto’s diffusion). The corresponding energy transfer parameters have been evaluated and discussed. Primarily, electrostatic dipole–dipole (s ~ 6) interactions are found to be responsible for the occurrence of energy transfer process in theses glasses.     

Performance of lithium-ion cells using 1 M LiPF<Subscript>6</Subscript> in EC/DEC (<Emphasis Type="Italic">v</Emphasis>/<Emphasis Type="Italic">v</Emphasis> = 1/2) electrolyte with ethyl propionate additive

In this work, 1 M LiPF₆:EC:DEC (v/v = 1/2) was used as a baseline electrolyte where EC is ethylene carbonate and DEC is diethyl carbonate. Ethyl propionate (EP) was used as an additive. The conductivity of the liquid electrolyte was obtained at ambient and elevated temperatures. The highest room temperature conductivity was observed at (8.05 ± 0.16) mS cm⁻¹ for the electrolyte containing 28.6 vol.% EP. Viscosity of the baseline and EP added baseline electrolytes have been measured at room and elevated temperatures. The electrolyte was also characterized by linear sweep voltammetry. The highest conducting electrolyte with 28.6 vol.% EP and the baseline electrolyte were used to fabricate several batteries. The batteries were charged and discharged at room temperature and at −20°C.     

High-power mid-IR (4–5 μm) femtosecond laser system with a broadband amplifier based on Fe<Superscript>2+</Superscript>:ZnSe

Concept of a solid-state femtosecond laser system with a multigigawatt power level in the 4–5 μm range has been proposed. The system contains an ultrashort pulse seeder, a two-stage chirped pulse amplifier based on a broadband Fe²⁺:ZnSe active element with optical pumping by a YSGG:Cr:Er laser, and an output stage that provides additional nonlinear optical compression of an amplified pulse to approximately 30 fs in a dielectric CaF₂ medium with anomalous group velocity dispersion in this spectral range.     

Enhanced electrical properties of polyethylene oxide (PEO) + polyvinylpyrrolidone (PVP):Li<Superscript>+</Superscript> blended polymer electrolyte films with addition of Ag nanofiller

Polymer blended films of polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):lithium perchlorate (LiClO₄) embedded with silver (Ag) nanofiller in different concentrations have been synthesized by a solution casting method. The semi-crystalline nature of these polymer films has been confirmed from their X-ray diffraction (XRD) profiles. Fourier transform infrared spectroscopy (FTIR) and Raman analysis confirmed the complex formation of the polymer with dopant ions. Dispersed Ag nanofiller size evaluation study has been done using transmission electron microscopy (TEM) analysis. It was observed that the conductivity increases when increasing the Ag nanofiller concentration. On the addition of Ag nanofiller to the polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ electrolyte system, it was found to result in the enhancement of ionic conductivity. The maximum ionic conductivity has been set up to be 1.14?×?10^?5 S cm^?1 at the optimized concentration of 4 wt% Ag nanofiller-embedded (45 wt%) polyethylene oxide (PEO)?+?(45 wt%) polyvinyl pyrrolidone (PVP):(10 wt%) Li⁺ polymer electrolyte nanocomposite at room temperature. Polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ +Ag nanofiller (4 wt%) cell exhibited better performance in terms of cell parameters. This is ascribed to the presence of flexible matrix and high ionic conductivity. The applicability of the present 4 wt% Ag nanofiller-dispersed polyethylene oxide (PEO)?+?polyvinyl pyrrolidone (PVP):Li⁺ polymer electrolyte system could be suggested as a potential candidate for solid-state battery applications. Dielectric constants and dielectric loss behaviours have been studied.