On the delay mechanism of Cl<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> diatomic anion dissociation up to the microsecond timescale

The dissociative capture of slow electrons by tetrachlorethylene (C₂Cl₄) has been investigated by resonant electron capture negative ion mass spectrometry. Metastable ions with fractional mass numbers 7.5, 17.5, and 19 corresponding to the C₂Cl₄⁻ → Cl⁻ + C₂Cl₃ and Cl₂⁻ → Cl⁻ + Cl decays occurring at the microsecond timescale have been detected. It has been revealed that Cl₂⁻ anions, which are fragment ions, can dissociate at the microsecond timescale, which is very surprising for a system with one internal degree of freedom. This process is assumingly attributed to the rotational excitation of Cl₂⁻ anions. Thus, the experimental estimate of the time of rovibronic relaxation in the Cl₂⁻ anion has been obtained.     

The structure of compositionally constrained zinc-ferrite spinel nanoparticles

ZnFe₂O₄ bulk material shows a normal-spinel structure and a closely defined composition at Zn²⁺/Fe³⁺ ≅ 0.5. However, the composition of zinc ferrite, prepared as nanoparticles, can be varied in a broad range without losing the single-phase spinel structure. In this article, structural mechanisms enabling this non-stoichiometry were studied using the X-ray absorption fine structure (EXAFS) in combination with X-ray diffractometry (XRD), transmission electron microscopy (TEM), and magnetic measurements. Nanoparticles with a narrow size distribution were synthesized using co-precipitation in water-in-oil microemulsions. First, the structure of the stoichiometric zinc-ferrite nanoparticles was studied in dependence of their size and the annealing temperature. EXAFS analysis showed that the degree of inversion x (as defined in the compound formula (Zn_1 − x Fe _x )[Fe_2 − x Zn _x ]O₄, with round and square brackets representing the tetrahedral and octahedral sites, respectively) increased with decreasing nanoparticles size. The structure of the stoichiometric nanoparticles and the nanoparticles of comparable size displaying Zn/Fe ratio of 0.2 (Fe-rich) and 0.7 (Zn-rich) were then compared. Analysis showed that the non-stoichiometry is structurally compensated predominantly in the core of the nanoparticle by the adjusted distribution of Zn and Fe ions over the two sublattices of the spinel structure.     

熔融Rb2ZnCl4的分子动力学模拟研究

采用在RbCl模拟和ZnCl₂模拟中选用的两体有效势，进行了晶态和熔融态Rb₂ZnCl₄的分子动力学模拟.模拟给出了Rb₂ZnCl₄ 6种径向分布函数，Zn-Cl和Rb-Cl间径向分布函数与新近的广延X射线吸收精细结构实验结果很好相符.在模拟产生的瞬态构型基础上进行了键序参数分析，研究了晶态和熔融态中的局部结构.模拟结果表明，Zn原子与其近邻Cl原子构成相当稳定的正四面体结构，并且熔融Rb_关键词：     

Interaction of chloride ions with water clusters absorbing ozone: A computer experiment

The molecular dynamics method is used to investigate the interaction of two, four, and six chloride ions with (H₂O)₅₀, clusters absorbing six ozone molecules. Chloride ions moving toward the cluster penetrate into it. The presence of ozone increases the residence time of Cl⁻ ions in the cluster. The duration of the perturbation increases with the number of Cl⁻ ions surrounding the 6O₃ + (H₂O)₅₀ system. The interaction with Cl⁻ ions enhances the positional disorder of the molecules in the system and enhances the intensity of absorption and emission of infrared radiation. These changes, however, are not monotonic function of the number of ions perturbing the system. As a result of the interaction with Cl⁻ ions, the integrated intensity of the Raman scattering on the (O₃)₆(H₂O)₅₀ cluster in the frequency range 0 ≤ ω ≤ 1100 cm⁻¹ is significantly lower and the number of peaks in the spectrum is smaller.     

Photoluminescence and multiphonon resonant Raman scattering in Ni-and Co-doped Zn1−x MnxTe crystals

Low-temperature photoluminescence, exciton reflection, and multiphonon resonant Raman scattering spectra of Ni-and Co-doped Zn_1−x Mn_xTe crystals were investigated. Intense emission occurs in a broad spectral region (1100–17 000 cm⁻¹) in the crystals containing Ni atoms. It is caused by intracenter transitions involving Mn²⁺ ions and transitions between the conduction band and a level of the doubly charged acceptor. The features of the exciton photoluminescence and multiphonon resonant Raman scattering involving longitudinal-optical (LO) phonons at various temperatures are investigated. The insignificant efficiency of the localization of excitons on potential fluctuations in the Zn_1−x Mn_xTe:Co crystals is established. A temperature-induced increase in the intensity of the 5LO multiphonon resonant Raman scattering line due to the approach of the conditions for resonance between this line and the ground exciton state is observed in these crystals. Fiz. Tverd. Tela (St. Petersburg) 40, 616–621 (April 1998)     

Vibrational spectra of (NH4)3ZnCl5

IR and Raman spectra of (NH₄)₃ZnCl₅ have been recorded. The observed spectra have been analysed on the basis of the vibrations of ZnCl ₄ ²⁻ and NH ₄ ⁺ ions. The appearance of multiple Raman bands indicates the presence of two different types of ammonium ions. The effect of anisotropic crystalline field over the ZnCl₄ and NH₄ tetrahedra is also discussed. The assignment of internal modes has been verified by the potential energy distribution calculations.     

M?ssbauer study of compounds of Cu3 ? xFexSnS4 and Cu2Fe1 ?xZnxSnS4 systems

A M?ssbauer study of the structural and charge states of ⁵⁷Fe and ¹¹⁹Sn atoms in the compounds of Cu_{3 −x} Fe _x SnS₄ and Cu₂Fe_{1 − x} Zn _x SnS₄ systems was performed. It was shown that the iron atoms in the compounds of both systems were in the divalent and trivalent states occupying the tetrahedral positions of the structure. The character of the changes of the degree of covalency of the Fe²⁺-S, Fe³⁺-S and Sn⁴⁺-S bonds during the isomorphic substitution in the systems was established.     

Raman spectroscopy of ionic liquids derived from 1‐n‐butyl‐3‐methylimidazolium chloride and niobium chloride or zinc chloride mixtures

Anionic species formed in mixtures of 1‐n‐butyl‐3‐methylimidazolium chloride (BMICl) with different amounts of niobium pentachloride (NbCl₅) or zinc dichloride (ZnCl₂) were investigated by Raman spectroscopy. In the BMICl and NbCl₅ ionic mixtures the presence of the anion NbCl₆⁻ was detected for all compositions (molar fraction, X) and a mixture of this anion and the neutral Nb₂Cl₁₀ in acid ones. Two different anions were observed for basic mixtures of BMICl and ZnCl₂: ZnCl₄²⁻(0 < X < 0.35) and Zn₂Cl₆²⁻(X > 0.3), whereas for acidic ones three species were detected: Zn₂Cl₆²⁻(X < 0.7), Zn₃Cl₈²⁻(X > 0.7) and Zn₄Cl₁₀²⁻(X > 0.7). It has also been observed that in both cases, the formation of larger anions causes a shift of the C H stretching modes to higher wavenumbers as the result of a decrease in the hydrogen bond between Cl and the hydrogens from the cation. Copyright © 2008 John Wiley & Sons, Ltd.     

Quadrupolar interaction in iridium cyanide mixed-ligands complexes in alkali halide matrices by ESR spectroscopy

Quadrupolar interactions in [IR(CN)₅]³⁻, [Ir(CN)₅Cl]⁴⁻ and [Ir(CN)₄Cl₂]⁴⁻ paramagnece a complexes in alkali halide host lattices are systematically analysed by ESR spectroscopy. The measured quadrupolar interactions are shown to have no clear correlation to the measured unpaired electron populations.     

Spectroscopic investigation of the plasma of a high-current diffuse discharge in He/Ar/CF2Cl2(CCl4) mixtures

Survey emission spectra in the region of 190–600 nm and time and service-life characteristics of a transverse nanosecond discharge in He/Ar/CF₂Cl₂(CCl₄) mixtures at a pressure of 10–100 kPa are investigated. In the emission spectra, excited products of the decomposition of freons—C₂(A−X), CN(B−X), Cl ₂ ^* , C^*, Cl^*, and Cl^+*— and the emission of ArF at λ=193 nm are revealed. The emissions of Cl ₂ ^* at λ=258 nm and ArF at λ=193 nm were the most intense. The discharge in the He/Ar/CF₂Cl₂ mixture is a multiwave emission source with λ=258 nm Cl ₂ ^* 193 nm ArF, and probably, 175 nm Arcl. It is of interest for applications in UV-VUV-range pulse photometry. The duration of the emission on Cl ₂ ^* , ArF, ArI, ClI, and ClII transitions in the discharge in the Ar/CF₂Cl₂ mixture (P=10–20 kPa) was 200–300 nsec. With adding He and increasing pressure to 100 kPa the duration of the emission decreased by a factor of 1.5–2. The basic mechanisms of the formation of Cl₂, ArF, and CN(B) molecules in the transverse-discharge plasma are considered. Uzhgorod State University, 46, Pidgirna Str., Uzhgorod, 294000, Ukraine. Translated from Zhurnal. Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 241–246, March–April, 1999.     

Spectroscopic characterization of metal chloride/polyamide complexes

Complexes formed between metal halides MX_n (M=Li, Zn, Fe; X=Cl, Br) and an amorphous polyamide have been characterized by Infrared and Raman spectroscopies. They provide examples of the large variety of situations which can be generated by varying the concentration of the salts and their Lewis acidity. The LiX salts are dissociated and the lithium ion interacts with four amide oxygens or less, depending on the concentration, while the anion establishes N-H...X⁻ hydrogen bonds. Complexes with LiTFSI exhibit some ionic conductivity. Zinc halides are complexed under the form of a bent ZnX₂ molecule strongly coordinated to two or one amide oxygens depending on the concentration. Finally, FeCl₃ is ionized in the whole investigated concentration range into FeCl ₄ ⁻ and FeCl₂(L) ₄ ⁺ where L is the amide ligand coordinated to iron by its oxygen. Paper presented at the 2nd Euroconference on Solid State Ionics in Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Kinetics of decomposition of the solid electrolyte RbCu4Cl3I2

The processes of electrochemical decomposition of the solid electrolyte RbCu₄Cl₃I₂ at the vitreous carbon electrode and chemical decomposition of RbCu₄Cl₃I₂ by iodine has been investigated. The anodic decomposition of the electrolyte occurs in two steps. At first, the oxidizing electrode reaction of Cu⁺ ions up to Cu²⁺ ions takes place at potentials higher than 0.57 V and onto the electrode surface the layer of decomposition products is formed, including the compound of divalent copper RbCuCl₃. Then the oxidizing reaction of I ions occurs at potentials higher than approximately 0.67 V with deposition of the iodine layer onto the electrode surface. The deposition rate of the layers of decomposition products is controlled by instantaneous nucleation and two-dimensional growth of the deposit. It was shown that slow diffusion of the iodine in the reaction product layer is a limiting step in the chemical interaction of iodine with RbCu₄Cl₃I₂. For the compressed RbCu₄Cl₃I₂ sample investigated, iodine diffusion coefficient was calculated to be 6.2×10⁻⁷ cm² s⁻¹. Iodine loss from the glassy carbon surface is about 1.1×10⁻⁴ g cm⁻² s⁻¹ at the thickness of the RbCu₄Cl₃I₂ sample is equal to 2 mm.     

Synthesis and ionic conduction of apatite-type materials

Apatite is a mineral with general formula M₁₀(XO₄)₆Z₂, where M are metallic elements such as Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ln³⁺ etc.; X=P, V, S, Si, Ge, Re, Cr etc; Z=F⁻, Cl⁻, I⁻, OH⁻, O²⁻, S²⁻ etc. Some materials with apatite structure (S.G. P6₃/m) exhibit quite high cationic (Li⁺, H⁺ etc.) and/or anionic (F⁻, Cl⁻ etc.) conduction. Recently, it was reported that some rare earth silicates, e.g., La₁₀(SiO₄)₆O₃, exhibit quite high oxide-ion conductivity. In this paper, we discuss chemical composition, structure, synthetic procedure and ionic conduction of apatite-type materials. Recent improvements are briefly reviewed. High ionic conductivity has been observed for both cation deficient, oxygen stoichiometric La_9.33(SiO₄)₆O₂ and cation stoichiometric, oxygen excess La₁₀(SiO₄)₆O₃ compositions. Grain boundary conductivity is usually low, which tends to dominate the impedance response. The resistance, particularly the grain boundary resistance is also found to depend on pO₂. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Study on the New Fluorescence Enhancement System of Tb –N-(2 - Pyridinyl) Ketoacetamide-Et<Subscript>3</Subscript>N-Zn and its Application

A sensitive fluorescence enhancement system was developed for the determination of zinc (II). The fluorescence intensity of the Tb- N- (2 - Pyridinyl) ketoacetamide (PKA) system was greatly enhanced by the addition of triethylamine (Et₃N) and zinc nitrate in the methanol solution. The excitation and emission wavelengths were 329 nm and 546 nm, respectively. Under optimal conditions, the fluorescence intensities varied linearly with the concentration of Zn²⁺ in the range of 8.0×10⁻⁷−5.0×10⁻⁶ M with a detection limit of 9.9×10⁻⁸ M. The interferences of some substances were described. This method was applied to the determination of amounts of Zn²⁺ in soybean, rice, and wheat, respectively. The results showed that the proposed procedure is a high selective, simple, and rapid method to the determination of Zn²⁺ ion. The mechanism of fluorescence enhancement was also studied.     

New insights into nanocomposite adsorbents for water treatment: A case study of polystyrene-supported zirconium phosphate nanoparticles for lead removal

By encapsulating zirconium phosphate (ZrP) nanoparticles into three macroporous polystyrene resins with various surface groups, i.e., −CH₂Cl, −SO₃ ⁻, and −CH₂N⁺(CH₃)₃ three nanocomposite adsorbents (denoted as ZrP–Cl, ZrP–S, and ZrP–N) were fabricated, respectively for lead removal from water. Effect of the functional groups on nano-ZrP dispersion and effect of ZrP immobilization on the mechanical strength of the resulting nanocomposites were investigated. The presence of the charged functional groups (−SO₃ ⁻ and −CH₂N⁺(CH₃)₃) are more favorable than the neutral −CH₂Cl group to improve nano-ZrP dispersion (i.e., to achieve smaller ZrP nanoparticles). ZrP–N and ZrP–S had higher capacity than ZrP–Cl for lead removal. As compared to ZrP–N, ZrP–S exhibits higher preference toward lead ion at high calcium levels as a result of the potential Donnan membrane effect. On the other hand, nano-ZrP immobilization would simultaneously reinforce both the compressive strength and the wear performance of the resulting nanocomposites with the ZrP loadings up to 5 wt%. The results reported herein would shed some light on the generation of environmental nanocomposites with high capacity and excellent mechanical strength.     

A Coumarin-Based Fluorescent Chemosensor for Zn<Superscript>2+</Superscript> in Aqueous Ethanol Media

A coumarin-based fluorescent chemosensor 1 for Zn²⁺ was designed and synthesized. Compound 1 exhibits lower background fluorescence due to intramolecular photoinduced electron transfer. However, upon mixing with Zn²⁺ in 30% (v/v) aqueous ethanol, a “turn-on” fluorescence emission is observed. The fluorescence emission increases linearly with Zn²⁺ concentration in the range 0.5–10 μmol L⁻¹ with a detection limit of 0.29 μmol L⁻¹. No remarkable emission enhancement was, however, observed for other metal ions. The proposed chemosensor was applied to the determination of Zn²⁺ in water samples with satisfactory results.     

Polarized absorption spectra of Co2+ in Na2Cd3Cl8 single crystals

Summary The polarized optical absorption spectra of Na₂Cd₃Cl₈: Co²⁺ in the range of 15 000 to 40 000 cm⁻¹ down to 15 K are reported. The Co²⁺ ion is found to occupy the Cd²⁺ sites in octahedral geometry and the spectra are interpreted satisfactorily in terms of a cubic ligand field model including spin-orbit coupling. The observed crystal field spectra are well reproduced withB=745 cm⁻¹,C=3410 cm⁻¹,Dq=700 cm⁻¹ and ζ (spin-orbit interaction) =520 cm⁻¹. No spectral evidence for tetragonal distortion is observed.     

Ion transport studies in zinc/cadmium halide doped silver phosphate glasses

A number of samples of silver phosphate glasses Ag₂O−P₂O₅−Zn/CdX₂ (X=Cl, Br or I) with 1, 5, 10 and 20 mol-% zinc or cadmium halides have been prepared. Control samples of undoped silver phosphate glasses were also prepared. These glasses were characterized by elemental analysis, X-ray diffraction, IR spectra, differential scanning calorimetry, transference number measurements and electrical conductivity studies. These glasses were found to be essentially ionic conductors. The undoped silver phosphate glass (Ag₂O−P₂O₅) has a low σ value in comparison to the doped ones. The conductivity (σ) in the doped glasses increases substantially with increasing concentration of dopant salts Zn/or CdX₂ and as the anions of the dopants are changed from Cl⁻ to I⁻. It is found that the σ values of the ZnX₂ doped glasses are slightly greater than those of the CdX₂ doped ones, and the silver phosphate glasses doped with (20 mol-%) Zn/CdI₂ yielded maximum conductivity. The results have been discussed and explained on the basis of changes in the structure of the glass matrix by the addition of dopant ions of different sizes, IR spectra and thermal studies.     

Structure and phase transitions in chloroantimonate(V) crystals: [(C2H5)3NH]SbCl6 and [(C2H5)3NH]SbCl6·1/2[(C2H5)3NH]Cl

New triethylammonium salts: [(C₂H₅)₃NH]SbCl₆ (TCA) and [(C₂H₅)₃NH]SbCl₆·1/2[(C₂H₅)₃NH]Cl (TCAT) have been synthesized. The compounds crystallise in monoclinic symmetry: space groups P2₁/n and P2₁/c, for TCA at 293 K and TCAT at 100 K, respectively. The crystal structure of [(C₂H₅)₃NH]SbCl₆ consists of discrete ionic pairs—triethylammonium cations and hexachloroantimonate anions—linked via the bifurcated N-H?Cl hydrogen bonds. The crystal structure of [(C₂H₅)₃NH]SbCl₆·1/2[(C₂H₅)₃NH]Cl is composed of three symmetrically independent triethylammonium cations, chlorine anion and two symmetrically independent hexachloroantimonate anions. TCA undergoes a structural phase transition at 336 K (on heating) into the orthorhombic C222 space group, whereas TCAT reveals a structural phase transition at 332 K. The phase transitions are of the first order type. TCA shows a ferroelastic domain structure below 336 K. Differential scanning calorimetry, dilatometric, dielectric dispersion and Raman scattering measurements have been used to study the phase transition mechanisms in these triethylammonium salts.     

LSP spectral changes correlating with SERS activation and quenching for R6G on immobilized Ag nanoparticles

In terms of chemical enhancement in Surface Enhanced Raman Scattering (SERS), we investigated the effect of halide and other anions to rhodamine 6G (R6G) adsorbed Ag particles that were immobilized on the substrates. The residual species on chemically prepared Ag particles such as citrate or a-carbon were thoroughly substituted by various anions, e.g., Cl⁻, Br⁻, I⁻, SCN⁻, CN⁻, or S₂O₃ ²⁻ anions, whose adsorption features are elucidated by the formation constants for AgX₂ ^(m−1)−, here X denotes the above anions. In particular, Cl⁻, Br⁻, or SCN⁻ ions activated SERS of R6G via intrinsic electronic interaction with Ag, whereas CN⁻, S₂O₃ ²⁻, or I⁻ anions quenched it due to their exclusive adsorption onto the Ag surfaces. We found that the activation process with the anions commonly yields a marked blue-shift of the coupled plasmon peak from ca. 650–700 to 500–550 nm in elastic scattering. It is rationalized by slight increase of the gap size between adjacent Ag nanoparticles by only ca. 1 nm based on theoretical simulations. This is probably caused by slight dissolution, oxidative etching, of the particles according to large formation constants of the complexes. Consequently, partly remaining negative charges on the Ag surface, and a slight increase in the gap size, providing huge electric field, facilitated R6G cations to adsorb on the nanoparticles, especially at the junction.