Resonanzramanspektrum und Struktur von matrixisoliertem Te3

Resonance Raman Spectrum and Structure of Matrixisolated Te₃ By condensing a mixture of 76% Te atoms and 24% Te₂ molecules in a nitrogen matrix at 15 K followed by annealing to nearly 25 K we obtained Te₃ molecules by a matrix reaction. The resonance Raman spectrum of Te₃ contains 8 overtones of the symmetric stretching vibration. The following values for ω₁ and x₁₁ have been calculated for the isotopically pure species ¹²⁶Te₃: ω₁ = 206.33 ± 0.15 cm^?1; x₁₁ = 0.24 ± 0.03 cm^?1 and ¹³⁰Te₃: ω₁ = 203.1 ± 0.2 cm^?1; x₁₁ = 0.22 ± 0.05 cm^?1. Using a 1:1 ratio of ¹²⁶Te and ¹³⁰Te in the synthesis of Te₃ the band shape of the envelopes of the superimposed spectra of all possible Te₃ species could only be explained assuming a bent structure (120° ± 10°). The value of the force constant f_r + f_rr of 210 ± 10 Nm^?1 reflects multiple bonding in this molecule. The proposed structure also agrees with thermodynamical considerations.     

b1σ+ and a1Δ emissions from group VIVI diatomic molecules bo+g å X21g emissions of Se2 and Te2

Chemiluminescence studies of the reaction microwave-discharged oxygen with D₂ Se and D₂ Te have led to the observation of the magnetic dipole transitions bO⁺_g å X₂1_g of Se₂ and Te₂ in the near infrared. The derived energies of the bO⁺_g states of Se₂ and Te₂ are 7960 ± 10 cm^?1 and 9596 ± 15 cm^?1, respectively.     

Determination of Total Selenium in Human Urine and Serum by Graphite-Furnace Atomic-Absorption Spectrophotometry with Palladium-Nickel-Ammonium Nitrates as a Matrix Modifier

After human urine or serum was diluted (1 + 9) with HNO₃ (0.2%, v/v) and standard additions of Se solution (100 μ L^?1), the diluted sample (10 μL) was introduced into the graphite cuvette. The matrix modifier [10μL, containing Pd (0.6 μg) + Ni (25 μg) + NH₄NO₃ (80 μg) in HNO₃ (0.2%, v/v) for urine, or Pd (0.3 μg) + Ni (30 μg) + NH₄NO₃ (80 μg) + Triton X-100 (0.04%) in HNO₃ (0.2%, v/v) for serum, respectively] was added and the mixture was heated according to a temperature program. The matrix modifier containing NH₄NO₃ in a suitable amount and a small amount of Pd enhanced the sensitivity for Se. The method detection limits (3σ) after dilution were about 4.9 ± 0.8 and 2.36 ± 0.18 μg L^?1 for urine and serum, respectively. The accuracy of this method was tested with SRM #2670 human urine Se and Seronorm Trace Elements #116 human serum Se, respectively, and the results of 97.6 – 101% and 100 – 104% were obtained with precision ± 0.3% and ± 2%, respectively. This method can be applied easily and accurately to the determination of concentration of total Se in human urine and serum.     

A laser flash photolysis/IR diode laser absorption study of the reaction of chlorine atoms with selected alkanes

A high‐resolution IR diode laser in conjunction with a Herriot multiple reflection flow‐cell has been used to directly determine the rate coefficients for simple alkanes with Cl atoms at room temperature (298 K). The following results were obtained: k(Cl + n‐butane) = (1.91 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐pentane) = (2.46 ± 0.12) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + iso‐pentane) = (1.94 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + neopentane) = (1.01 ± 0.05) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐hexane) = (3.44 ± 0.17) × 10^?10 cm³ molecule^?1 s^?1 where the error limits are ±1σ. These values have been used in conjunction with our own previous measurements on Cl + ethane and literature values on Cl + propane and Cl + iso‐butane to generate a structure activity relationship (SAR) for Cl atom abstraction reactions based on direct measurements. The resulting best fit parameters are k_p = (2.61 ± 0.12) × 10^?11 cm³ molecule^?1 s^?1, k_s = (8.40 ± 0.60) × 10^?11 cm³ molecule^?1 s^?1, k_t = (5.90 ± 0.30) × 10^?11 cm³ molecule^?1 s^?1, with f( ? CH₂^? ) = f (? CH₂^? ) = f (?C?) = f = 0.85 ± 0.06. Tests were carried out to investigate the potential interference from production of excited state HCl(v = 1) in the Cl + alkane reactions. There is some evidence for HCl(v = 1) production in the reaction of Cl with shape n‐hexane. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 86–94, 2002     

A Raman spectroscopic study of the low-frequency vibrations in anisole and anisole-d3

Low-frequency Raman spectra of solid anisole and of solid anisole-d₃ have been recorded at 130 K. The phenyl torsion observed at 148 cm^?1 is shifted to 133 cm^?1 upon deuteration of the methyl group. The twofold torsional barriers calculated from these frequencies are 4033 ± 110 cm^?1 and 4094 ± 123 cm^?1 indicating that coupling to other low-frequency modes in both cases is of the same order of magnitude. The methyl torsional mode was observed at 285 cm^?1 in the spectrum of solid anisole and at 183 cm^?1 in the spectrum of anisole-d₃. The threefold barriers calculated using these frequencies are 1847 ± 20 cm^?1 and 1465 ± 18 cm^?1 respectively. These barrier values indicate that the methyl torsion is coupled to another low-frequency mode. A doublet centered at 230 cm^?1 in anisole is shifted to 245 cm^?1 in anisole-d₃; it is proposed that this is due to a ring mode coupled to the methyl torsion. The splitting is interpreted as an example of Davydov splitting.     

Interatomic potential for the X1Σ state of Be2, revisited

An extended geminal model has been applied to determine the interatomic potential for the X¹Σ state of Be₂. By adopting a (23s, 10p, 8d, 6f, 3g, 2h) uncontracted Gaussian‐type basis, the following spectroscopic parameters are obtained: R_e = 4.633 a.u. (4.63 a.u.), D_e = 945 ± 15 cm (790 ± 30 cm), G(1)–G(0) = 221.7 cm^?1 (223.8 ± 2 cm^?1), G(2)–G(1) = 175.0 cm^?1 (169 ± 3 cm^?1), G(3)–G(2) = 123.1 cm^?1 (122 ± 3 cm^?1), and G(4)–G(3) = 80.8 cm^?1 (79 ± 3 cm^?1), experimental values in parentheses. The calculated binding energy is substantially higher than the accepted experimental value. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Two‐Plateau Li‐Se Chemistry for High Volumetric Capacity Se Cathodes

For Li‐Se batteries, ether‐ and carbonate‐based electrolytes are commonly used. However, because of the “shuttle effect” of the highly dissoluble long‐chain lithium polyselenides (LPSes, Li₂Se_n, 4≤n≤8) in the ether electrolytes and the sluggish one‐step solid‐solid conversion between Se and Li₂Se in the carbonate electrolytes, a large amount of porous carbon (>40 wt % in the electrode) is always needed for the Se cathodes, which seriously counteracts the advantage of Se electrodes in terms of volumetric capacity. Herein an acetonitrile‐based electrolyte is introduced for the Li‐Se system, and a two‐plateau conversion mechanism is proposed. This new Li‐Se chemistry not only avoids the shuttle effect but also facilitates the conversion between Se and Li₂Se, enabling an efficient Se cathode with high Se utilization (97 %) and enhanced Coulombic efficiency. Moreover, with such a designed electrolyte, a highly compact Se electrode (2.35 g_Se cm^?3) with a record‐breaking Se content (80 wt %) and high Se loading (8 mg cm^?2) is demonstrated to have a superhigh volumetric energy density of up to 2502 Wh L^?1, surpassing that of LiCoO₂.     

Spectra of inert-gas matrices containing bismuth: ground-state frequency of Bi2

Bi, Bi₂, Bi₄, and possibly Bi₃ in inert-gas matrices were observed and characterized. Their spectra exhibit negligible shifts from matrix to matrix and, when known, from gas to matrix. The Bi₂ Raman frequency in Ne is measured at 173 ± 1 cm^?1, in excellent agreement with the gas phase.     

Synthese und Kristallstruktur von [Se3N2Cl]+ GaCl4−

Synthesis and Crystal Structure of [Se₃N₂Cl]⁺GaCl₄^? [Se₃N₂Cl]⁺GaCl₄^? has been prepared by the reduction of [Se₂NCl₂]⁺GaC1₄^? with SbPh₃ in CH₂Cl₂ solution, forming red crystals, which were characterized by an X-ray structure determination. Space group P2₁/n, Z = 4, 1640 observed unique reflections, R = 0.050. Lattice dimensions at ? 80 °C: a = 929.4(1), b= 1078.8(1), c = 1135.7(1) pm, β = 92.026(9)°. The cations from nearly planar Se₃N₂ five membered rings with Se? N bond lengths from 170 to 176pm and a Se? Se bond of 242.2 pm. One of the selenium atoms is bonded to the chlorine atom.     

Kinetics of FeSe2 oxidation by ferric iron and its reactivity compared with FeS2

The mobility and bioavailability of selenium is a major health and environmental issue and a main concern for geological disposal of high-level radioactive waste. Chemically and/or microbially mediated oxidation of insoluble Se-bearing particulate, such as iron selenides, to dissolved and mobile phases controls the transport and distribution of Se in the environment. The oxidation of ferroselite(FeSe2) by ferric iron was investigated in anoxic conditions. The redox reaction can be represented by: FeSe2 + 2Fe3+ = 2Se0 + 3Fe2+. Kinetic studies indicated that the reaction can be described by second-order rate law, with rate constants of 0.49±0.01, 0.85±0.02, 1.84±0.04, and 3.29±0.13 L mol-1 s-1 at pH 1.62, 1.87, 2.23, and 2.49, respectively. The positive correlation between reaction rate and pH implies that diffusion of Fe3+ oxidant to the mineral surface is the rate-determining step. The strong reactivity of FeSe2 towards Fe3+ suggests that ferric iron may play a significant role in FeSe2 oxidation process(e.g., by Se4+, O2, etc.) and Se0 should be the first reaction product. Also, it was shown that the reduction rate of Fe3+ or Se4+ by pyrite(FeS2) can be significantly increased in the presence of FeSe2, suggesting a stronger reactivity of FeSe2 compared with pyrite. The results obtained extend our knowledge about the subtle interaction between Se, pyrite and iron selenides in the environment, and give insight into the transfer of selenium from iron selenides to bio-available selenium(i.e., selenite and selenate) in the Se-rich environment.     

Near infrared electronic spectrum of TCNQ mono-valent anion

The high resolution near infrared electronic spectrum of TCNQ anion dissolved in 2-methyltetrahydrofuran glass at 77 K has been determined. The absorption bands are interpreted as simple progressions of two molecular vibrations in a single electronic excited state with ν₀₀ = 11661 cm^?1. The molecular vibrations (ω′₁ = 1264 ± 3 cm^?1, ω′₂ = 335 ± 3 cm^?1) of the vibrational progression agree well with observed Raman active transitions. The experimental data do not require the presence of two electronic transitions in the 1.3 to 2.1 eV region, contrary to what had been assumed previously on the basis of less well resolved room temperature spectra.     

Rate coefficients and mechanisms of the reaction of cl‐atoms with a series of unsaturated hydrocarbons under atmospheric conditions

Rate coefficients and/or mechanistic information are provided for the reaction of Cl‐atoms with a number of unsaturated species, including isoprene, methacrolein ( MACR ), methyl vinyl ketone ( MVK ), 1,3‐butadiene, trans‐2‐butene, and 1‐butene. The following Cl‐atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10^?10cm³ molecule^?1 s^?1 (independent of pressure from 6.2 to 760 Torr); k( MVK ) = (2.2 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k( MACR ) = (2.4 ± 0.3) × 10^?10 cm³ molecule^?1 s^?1; k(trans‐2‐butene) = (4.0 ± 0.5) × 10^?10 cm³ molecule^?1 s^?1; k(1‐butene) = (3.0 ± 0.4) × 10^?10 cm³ molecule^?1 s^?1. Products observed in the Cl‐atom‐initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH₂O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1‐chloro‐3‐methyl‐3‐buten‐2‐one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO₂ (58 ± 5%), CH₂O (47 ± 7%), CH₃OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK ; CO (52 ± 4%), chloroacetone (42 ± 5%), CO₂ (23 ± 2%), CH₂O (18 ± 2%), and HCOCl (5%) from MACR ; CH₂O (7 ± 1%), HCOCl (3%), acrolein (≈3%), and 4‐chlorocrotonaldehyde (CCA, not quantified) from 1,3‐butadiene; CH₃CHO (22 ± 3%), CO₂ (13 ± 2%), 3‐chloro‐2‐butanone (13 ± 4%), CH₂O (7.6 ± 1.1%), and CH₃OH (1.8 ± 0.6%) from trans‐2‐butene; and chloroacetaldehyde (20 ± 3%), CH₂O (7 ± 1%), CO₂ (4 ± 1%), and HCOCl (4 ± 1%) from 1‐butene. Product yields from both trans‐2‐butene and 1‐butene were found to be O₂‐dependent. In the case of trans‐2‐butene, the observed O₂‐dependence is the result of a competition between unimolecular decomposition of the CH₃CH(Cl)? CH(O?)? CH₃ radical and its reaction with O₂, with k_decomp/k_O2 = (1.6 ± 0.4) × 10¹⁹ molecule cm^?3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol^?1. The variation of the product yields with O₂ in the case of 1‐butene results from similar competitive reaction pathways for the two β‐chlorobutoxy radicals involved in the oxidation, ClCH₂CH(O?)CH₂CH₃ and ?OCH₂CHClCH₂CH₃. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334–353, 2003     

Temperature dependence of radiationless processes. Isoquinoline in solution

The temperature dependence of the fluorescence quantum yield φ_f, the fluorescence lifetime τ_f, and the oscillator strength f(S₀→S₁) of isoquinoline in solution has been measured between room temperature and 77 K. Following an Arrhenius type expression, φ_f in ethanol increases from 0.012±0.002 at 295 K to 0.61±0.03 at 77 K paralleled by an increase of τ_f from 0.25±0.10 ns to 9.0±0.2 ns. Over the same temperature range f(S₀→S₁) and the radiative fluorescence lifetime remain constant. By analyzing the temperature dependent data, it is shown that a spin-allowed internal conversion process with an activation energy of ～1500 cm^?1 is responsible for the observed temperature effect. A mechanism is proposed based upon a thermally activated depopulation of the S₁(ππ^*) state of isoquinoline via a slightly higher state, presumably the S₂(ππ^*) singlet state. An extremenly fast process involving the dissociation of the hydrogen bond deactivates this latter state, by possing S₁.     

A study of helix formation in polydimethysiloxane by Raman scattering

Depolarization ratios ρ of the Raman bands due to CH₃ stretching at 2907 cm^?1 and the Si? O skeletal mode at 491 cm^?1 have been measured in polydimethylsiloxane gum as a function of temperature from 100°C to ?45°C. Below 0°C the changes in p have been interpreted in terms of the formation of helical regions in the gum. The enthalpy of helix formation ΔH has been determined as 3200 ± 600 cal/mole. An upper limit on the entropy change, ΔS, of 16 ± 3 e.u./mole and minimum values of helix content at different temperatures have been found. The Raman spectrum of crystalline polydimethylsiloxane is presented.     

High Na+ Mobility in rGO Wrapped High Aspect Ratio 1D SbSe Nano Structure Renders Better Electrochemical Na+ Battery Performance

We chose to understand the cyclic instability and rate instability issues in the promising class of Na⁺ conversion and alloying anodes with Sb₂Se₃ as a typical example. We employ a synthetic strategy that ensures efficient rGO (reduced graphene oxide) wrapping over Sb₂Se₃ material. By utilization of the minimum weight of additive (5 wt.% of rGO), we achieved a commendable performance with a reversible capacity of 550 mAh g⁻¹ at a specific current of 100 mA g⁻¹ and an impressive rate performance with 100 % capacity retention after high current cycling involving a 2 Ag⁻¹ intermediate current step. The electrochemical galvanostatic intermittent titration technique (GITT) has been employed for the first time to draw a rationale between the enhanced performance and the increased mobility in the rGO wrapped composite (Sb₂Se₃-rGO) compared to bare Sb₂Se₃. GITT analysis reveals higher Na⁺ diffusion coefficients (approx. 30 fold higher) in the case of Sb₂Se₃-rGO as compared to bare Sb₂Se₃ throughout the operating voltage window. For Sb₂Se₃-rGO the diffusion coefficients in the range of 8.0×10⁻¹⁵ cm² s⁻¹ to 2.2×10⁻¹² cm² s⁻¹ were observed, while in case of bare Sb₂Se₃ the diffusion coefficients in the range of 1.6×10⁻¹⁵ cm² s⁻¹ to 9.4×10⁻¹⁵ cm² s⁻¹ were observed.     

Volumes of activation for the reactions of Pentacyanocobaltate(III) Complexes in aqueous solution

The volumes of activation in cm³ mol^?1 for the aquation of Co(CN)₅X^3? were determined at 40°C and μ = 1 M (NaClO₄) to be + 7.8 ± 0.5 for X = Cl^?, + 7.6 ± 0.6 for X = Br^?, + 14.0 ± 0.7 for X = I^?, and + 16.8 ± 0.5 for X = N₃^? (0.1 M HClO₄), respectively. The volumes of activation for the aquation of Co(CN)₅Cl^3? at μ = 0.1 M are + 10.0 ± 0.6 cm³ mol^?1 and ± 9.1 ± 0.3 cm³ mol^?1 at 40°C and 25°C, respectively. The corresponding values for the anation of Co(CN)₅OH₂^2? (at 40°C) and μ = 1 M by Br^?, I^?, and NCS^? are +8.4 ± 1.0, +9.4 ± 1.6, and +8.2 ± 0.9 cm³ mol^?1, respectively. These data are discussed in terms of a dissociative (D) mechanism.     

Spectra and structure of small ring compounds: Part XXXVIII. Cyclobutanol

The Raman spectrum of gaseous cyclobutanol has been recorded and the far infrared spectrum of the gas has been obtained at a resolution of 0.5 cm^?1. At least six Q-branches arising from the low frequency ring-puckering motion have been observed and assigned on the basis of a potential of the form V(X) = (6.32 ± 0.21) × 10⁵X⁴?(4.18 ± 0.04) × 10⁴X²+ (8.81 ± 1.20) × 10³X³ with a reduced mass of 170 amu. An energy difference between the equatorial and axial forms was found to be 50–150 cm^?1 with the equatorial being more stable and a barrier of 700–900 cm^?1 was found for the interconversion. Three O-H stretching modes were observed in the Raman spectrum. It is concluded that the O-H moiety has both the gauche and trans conformations present in the equatorial form but only the gauche conformer is present in the axial form of the ring. Three O-H torsional modes were observed at 244 (trans conformer), 226.5 and 181.5 cm^?1 (gauche conformer) for the equatorial form and one O-H torsion at 237.5 cm^?1 (gauche conformer) for the axial form. The potential function governing the O-H torsional motion for the equatorial form was found to be V₁ = 280 ± 7 cm^?1 (800 cal mole^?1) and V₃ = 425 ± 3 cm^? (121.5 cal mole^?1) with the trans conformer being more stable than the gauche by approximately 206 cm^?1 (589 cal mole^?). The barriers to trans-gauche and gauche-gauche interconversion have essentially the same values, 500 cm^?1 (1430 cal mole^?1).     

Spectra and structure of organophosphorus compounds: XVII. Infrared and Raman spectra. vibrational assignment and barriers to internal rotation for t-butylphosphine

The infrared spectra of gaseous and solid tertiary-butylphosphine, [(CH₃)₃CPH₂], have been recorded from 50 cm^?1 to 3500 cm^?1. The Raman spectra of gaseous, liquid and solid (CH₃)₃CPH₂ have been recorded from 10 to 3500 cm^?1. A vibrational assignment of the 42 normal modes has been made. A harmonic approximation of the methyl torsional barrier from observed transitions in the solid state gave a result of 4.22 kcal mol^?1 and 3.81 kcal mol^?1 in the gaseous state. Hot band transitions for the phosphino torsional mode have been observed. The potential function for internal rotation about the C-P bond has been calculated. The two potential constants were determined to be: V₃ = 2.79 ± 0.01 kcal mol^?1 and V₆ = 0.07 ± 0.01 kcal mol^?1.     

A Novel Tantalum Cluster Chalcohalide Ta4S1.5Se7.5I8

Single crystals of Ta₄S_1.5Se_7.5I₈ are obtained by heating Ta, S, Se and I₂ at 300 °C in 4.0:1.0:8.0:4.4 molar ratio. The structure was determined by X-ray analysis and consists of molecular clusters [Ta₄(μ₄-S)(μ₂-Q_axSe_eq)₄I₈] (Q ≈ Se_0.87S_0.13). The tantalum atoms form a square with long Ta…Ta distances (3.26–3.32 Å), with four dichalcogenide ligands bridging the Ta–Ta edges and a sulfur atom capping the square. Each Ta atom has two terminal iodine atoms. Raman spectroscopy study shows the presence of the characteristic absorption band at 396 cm^?1 which is due to the Ta₄–μ₄-S vibrations. Cyclic voltammetry shows that Ta₄S_1.5Se_7.5I₈ in solid state undergoes quasi-reversible one-electron oxidation which is metal-centered.