A multipurpose efficient tunable infrared coherent source with tuning range from 0.8 to 25 μm and peak powers in the range 50–200 kw

We have developed in the last 2 years a multipurpose efficient tunable coherent source in the near- and mid-infrared, with high level beam quality and stability requirements.This complex device makes use of a high reliability home-made YAG: Nd³⁺ laser as primary power source, associated with a 1.06 μm pumped infrared dye laser (i.r. dye), a lithium niobate optical parametric oscillator (OPO), two optical mixer crystals, gallium selenide (GaSe) and cadmium selenide (CdSe) and a lithium niobate doubler.At the present time, the following wavelength ranges have been covered: 1.08–1.20 μm and 9–19 μm starting from the i.r. dye, and 1.6–3.6 μm, 0.8–1.8 μm and 2.6–25 μm starting from the OPO. According to the wavelength the peak powers extend from 50 W to 200 kW.     

Semiempirical assignment of the electron transitions in manganese(II)-doped II–VI compounds

The electron transitions in manganese(II)-doped II–VI compounds have been assigned by the Angular Overlap Model (AOM). The extracted AOM and electron repulsion parameters are applied to assess the covalency of the respective manganese-ligand bonds. A comparison with Crystal Field Theory (CFT) is made in order to demonstrate the advantages offered by the AOM. The Dq values for Mn(II) in CdS and CdSe were found by interpolation from the Dq vs R⁻⁵_ml relation.     

Superconductivity and ferromagnetism in EuFe?(As(1-x)P(x))?

Superconductivity and ferromagnetism are two antagonistic cooperative phenomena, which makes it difficult for them to coexist. Here we demonstrate experimentally that they do coexist in EuFe?(As(1-x)P(x))? with 0.2 ≤ x ≤ 0.4, in which superconductivity is associated with Fe 3d electrons and ferromagnetism comes from the long-range ordering of Eu 4f moments via Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. The coexistence features large saturated ferromagnetic moments, high and comparable superconducting and magnetic transition temperatures, and broad coexistence ranges in temperature and field. We ascribe this unusual phenomenon to the robustness of superconductivity as well as the multi-orbital character of iron pnictides.     

Spectra-Structure Correlations in 2,2′-Bipyridine Mercury(II) Saccharinate: Comparison With Mercury(II) Saccharinate And Chloromercury(II) Saccharinate∗

Abstract

The infrared spectrum of 1:1 complex of mercury(II) saccharinate with 2,2′-bipyridine, [Hg(C₇H₄NO₃S)₂(C₁₀H₈N₂)], was studied in the CO and SO₂stretching regions. The appearance of the spectrum in the region of the carbonyl stretching modes was correlated with the number of non-equivalent CO groups in the structure. The spectral and structural characteristics of the CO groups in the title compound were compared with the corresponding ones in the mercury(II) saccharinate and chloromercury(II) saccharinate. It was found that the frequency of the CO stretchings in the spectrum of Hg(bpy) (sac)₂ is significantly lower (1630 and 1615 cm^?1) than the frequency of the corresponding modes in the spectra of covalently bonded mercury(II) saccharinate (1705 and 1680 cm^?1) and chloromercury saccharinate (1694 cm^?1). An attempt was also made to assign the bands which are mainly due to the symmetric and the antisymmetric SO₂ stretching vibrations.

     

Investigation of the reaction e+e− → ηπ+π− in the energy range up to 1.4 GeV

The reaction e⁺e⁻ → ηπ⁺π⁻ has been studied with the Neutral Detector in the CM energy range 1.05–1.40 GeV at VEPP-2M. At the maximum energy the cross section exceeds the prediction of the vector dominance with one ϱ(770). The following upper limits for the electron width times branching ratio into ηπ⁺π⁻ have been obtained for a resonance with a mass of 1.28 GeV and width of 0.08 GeV observed with the Omega-spectrometer at CERN: Λ_ee·B_ηππ < 9 eV, and for a ϱ′(1250) with a mass of 1.26 GeV and width of 0.125 GeV: Λ_ee·B_ηππ < 14 eV at 90% confidence level.     

High-temperature ferromagnetism in Si1 ? x Mn x (x ≈ 0.5) nonstoichiometric alloys

It has been found that the Curie temperature (T _C ?? 300 K) in nonstoichiometric Si_{1 ? x} Mn _x alloys slightly enriched in Mn (x ?? 0.52?C0.55) in comparison to the stoichiometric manganese monosilicide MnSi becomes about an order of magnitude higher than that in MnSi (T _C ?? 30 K). Deviations from stoichiometry lead to a drastic decrease in the density of charge carries (holes), whereas their mobility at about 100 K becomes an order of magnitude higher than the value characteristic of MnSi. The high-temperature ferromagnetism is ascribed to the formation of defects with the localized magnetic moments and by their indirect exchange interaction mediated by the paramagnetic fluctuations of the hole spin density. The existence of defects with the localized magnetic moments in Si_{1 ? x} Mn _x alloys with x ?? 0.52?C0.55 is supported by the results of numerical calculations performed within the framework of the local-density-functional approximation. The increase in the hole mobility in the nonstoichiometric material is attributed to the decay of the Kondo (or spin-polaron) resonances presumably existing in MnSi.     

Photo-induced effect in the layered perovskite manganite La_(1.2)Sr_(1.8)Mn_(1.8)Co_(0.2)O_7

1IntroductionWiththediscoveryofcolossalmagnetoresistance(CMR)effectinmanganites,hole-dopingperovskitemanganiteswithunusualelectronictransportandmagneticpropertieshaveattractedconsiderableattention.Thesepropertiesresultfromanintrinsicinteractionbetweencharge,spin,orbitalandlatticedegreesoffreedomthatarestronglycoupledtoeachother[1—6].DoubleexchangemodelcombinedwithJohn-Tellereffectwasusedtoexplainthesepropertiespartly[7—9].InordertogetbetterunderstandingofthemechanismofCMReffect,externals…     

The Application of Infrared Spectra to Structural Problems in Copper(II) Complexes of 2,2′-Bipyridine

The infrared spectra of the complexes [Cu(bipy)₃] (C10₄)^2′ [Cu(bipy)₂] (C10₄)₂, [Cu(bipy)₂I]I, [cu(bipy)₂I] C10₄ and [Cu(bipy)(C10₄)₂] (bipy - 2,2′-bipyridine) are discussed in relation to their known or probable structures. Evidence for tetragonal distortion of [Cu(bipy)₃]₂₊ but not [Cu(phen)₃]₂₊ (phen = 1, 10-phenanthroline) is adduced.     

Transformation from δ-FeOOH to hematite in the presence of trace Fe(II)

δ-FeOOH, a poorly crystalline iron oxyhydroxide, can transform to the more stable iron oxyhydroxide or oxide. In the present work, the transformation from δ-FeOOH to goethite and hematite in the presence of trace Fe(II) has been investigated. The results show that Fe(II) can catalyze this transformation of δ-FeOOH. Based on experimental results and literature data, it is confirmed that two transformation mechanisms exist in the current system. One is the catalytic dissolution of δ-FeOOH, which leads to the formation of both hematite and goethite. The other is the catalytic solid-state transformation from δ-FeOOH to hematite. Which mechanism predominates depends on the temperature, pH, heating rate, etc. The results reveal that high temperatures (in the range from room temperature (RT) to 100 °C) favor the solid-state transformation as well as the formation of hematite. Given the structural relationships observed between δ-FeOOH and hematite, it is possible that the solid-state transformation from δ-FeOOH to hematite can exist.     

Measurement of the total cross section difference ΔσT(pp) in the energy range from 0.43 to 2.4 GeV

The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference Δσ_T = −2σ_{1 tot} at 26 energies between 0.43 and 2.4 GeV. Here Δσ_T is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ_1tot is one of spin-dependent terms in the total cross section σ_tot. The energy dependence of Δσ_T below 1 GeV shows similar structures as for Δσ_L. An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.     

The ferromagnetic to antiferromagnetic transition in La1−x Y x Mn2Si2(57Fe) compounds

A set of La_1–xY_xMn₂Si₂(⁵⁷Fe) samples withx=0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.5 and 1.0 have been prepared with the tetragonal ThCr₂Si₂ structure.⁵⁷Fe Mössbauer spectra have been collected at 4.2 K for all samples. The spectra can be well fitted by two sextets, the predominant one (90% of the spectral area) being associated with⁵⁷Fe atoms in the Mn 4d site, with the remainder located in the Si 4e site. The analysis shows that there are distinct changes in the hyperfine interaction parameters for samples above and below the critical concentrationx _c 0.15, at which a transition from ferromagnetism to antiferromagnetism occurs. This transition is a result of a change in the exchange interactions linked with changes in the interatomic distances, due to the smaller atomic volume of Y compared to that of La.On leave from Applied Acoustics Institute, Shaanxi Teachers University, Xian, PR China.     

The Spectrochemical Properties of bis-(α-Methioninephosphonato)Copper(II) in Aqueous Solution

The combined results of spectrophotometric measurements and e.s.r. spectra, as well as those obtained from potentiometric titration studies, are used to determine the structure of the individual complex species formed between copper(II) ion and 1-amino-3-methylthiopropane-phosphonic acid (α-MetP) in aqueous solution. The e.s.r. parameters are typical for CuN₂O₂ coordination geometries. The d-d absorption spectrum of [Cu(α-MetP)₂]^2-chromofore in aqueous solution has been treated by the Angular Overlap Model in C_2h, symmetry. Low-symmetry splittings of the broad asymmetric absorption band in the measured spectrum were found by Gaussian analysis. The effect of the σ-and π-bonding of bidentate ligand upon the central ion d-orbital energies is destribed in a ligand-field framework.     

Spin-glass state and ferromagnetic order in Cu(II)－Fe(III) cyanides

The static and dynamic magnetic properties of a Prussian blue analogue, molecular magnet Cu^Ⅱ_{3}[Fe^Ⅲ(CN)_6]_2·3NH_3·6H_2O were investigated in detail. The H dependence of the linear AC susceptibility, the irreversibility in the field-cooled (FC)/zero-field-cooled (ZFC) magnetization (M_{FC}/M_{ZFC}) and the relaxation of M_{ZFC} suggest that the magnetic system can be visualized as containing a ferromagnetic cluster of spin below T_C, mixed with small spin-glass clusters formed below temperature T_g less than T_C. The observed magnetic properties are explained with a ferromagnetic-spin-glass phase model. The magnetic ordering of the sample occurs below 19.8K.     

A New Rhodamine-Based “Off-On” Fluorescent Chemosensor for Hg (II) Ion and its Application in Imaging Hg (II) in Living Cells

A novel rhodamine derivative (Rh-C), synthesized by the reaction of rhodamine ethylenediamine and cinnamoyl chloride, was evaluated as a chemoselective Hg(2+) ion sensor. Addition of Hg(2+) to an ethanol aqueous solution of the Rh-C resulted in a color change from colorless to obvious pink color together with distinctive changes in UV-vis absorption spectrum and fluorescence spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The interaction of Hg(2+) and sensor Rh-C was proven to adopt a 1:1 binding stoichiometry and the recognition process is reversible. The chemosensor displayed a linear response to Hg(2+) in the range of 0.4-5?μM with a detection limit of 7.4?×?10(-8)?M. The sensor Rh-C was also successfully applied to the imaging of Hg(2+) in HL-7702 cells.     

Compression behavior of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) bulk metallic glass up to 24 GPa

With the development of multicomponent Zr-based glass bulk metallic glasses(BMGs) with a larger geometry by a conventional casting process with a low coolingrate[1—4], high pressure, which is the simplest way to vary the interatomic distance ofsubstance and thus change its physical properties, has been employed as an importantmeans to investigate structural relaxation and the crystallization of the BMGs[5]. Relativeto crystalline, metallic glasses have excess free volume, which will annihil…