Anharmonicity in rotational and vibrational excitation of H2 by Li+ collisions

Integral cross sections for pure rotational and vibrational-rotational excitation of H₂(X¹Σ⁺_g) by Li⁺(¹S) impact are computed by close-coupling methods at 0.2, 0.6, and 1.2 eV in the c.m. system using vibrational functions that are numerical solutions of the one-dimensional radial Schrödinger equation for harmonic, Morse, and adiabatically corrected Kolos-Wolniewicz (KW) potential functions. Comparison of results employing KW and Morse functions shows excellent agreement for all transitions studied. Findings using harmonic oscillator functions, however, differ noticeably from KW and Morse values for vibrational (0 → 1) and very large rotational (Δj = 10) transitions, but are satisfactory for lower order (0 → 2, 4, 6, 8) rotational transitions.     

Conductivity,structure, and thermal properties of chitosan‐based polymer electrolytes with nanofillers

This paper focus on the effect of nanosize (<50 nm BET) inorganic alumina (Al₂O₃) filler on the structural, conductivity, and thermal properties of chitosan‐based polymer electrolytes. Films of chitosan and its complexes were prepared using solution‐casting technique. Different amounts of Al₂O₃ viz., 3, 4.5, 6, 7.5, 9, 12, and 15 wt% were added to the highest room temperature conducting sample in the chitosan–salt system, i.e. sample containing 60 wt% chitosan–40 wt% NH₄SCN. The conductivity value of the sample is 1.29 × 10^?4 S cm^?1. On addition of 6 wt% Al₂O₃ filler the ionic conductivity increased to 5.86 × 10^?4 S cm^?1. The amide and amino peaks in the spectrum of chitosan at 1636 and 1551 cm^?1, respectively, shift to lower wavenumbers on addition of salt. The glass transition temperature T_g for the highest conducting composite is 190°C. The increase in T_g with increase in more than 6 wt% filler content is attributed to the increase in degree of crystallinity as proven from X‐ray diffraction studies. Copyright © 2009 John Wiley & Sons, Ltd.     

Complete TDA and RPA Calculations on the Electronic Transitions of Fullerene‐C60 in the CNDO/S and INDO/S Approximations*

Complete single‐excitation mixing calculations on the electronic transitions of the icosahedral C₆₀ molecule have been carried out with the Tamm–Dancoff approximation (TDA) and random‐phase approximation (RPA) schemes in the CNDO/S and INDO/S approximations. The complete space of 14,400 (1p–1h) pairs is partitioned into subspaces classified according to the irreducible representations of the Ih group. For this purpose, matrix representations of the group generators are obtained on a fixed set of basis functions and are used to construct the projection operators. Degenerate molecular orbitals in each energy level are symmetry‐adapted to these projection operators. Degenerate (1p–1h) pairs or singly excited configuration wave functions are similarly symmetrized. In addition, the Clebsch–Gordan coefficients are obtained and listed in an Appendix. The TDA and RPA equations are then solved for each irreducible representation separately. Both schemes with the projection operators and with the Clebsch–Gordan coefficients gave the same results as expected, indicating that the calculations were correctly done. The transition energies from the ground state 1¹A_g to low‐lying singlet and triplet excited states and the oscillator strengths for the allowed transitions (n¹T_1u–1¹A_g) are given in tables. A proper way to normalize is discussed for the eigenvectors of the RPA‐type matrix equation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Molecular zeeman effect in NH3

High-resolution measurements of ΔM_j = 0 inversion transitions in ¹⁴NH₃ in 100 kG magnetic fields were made using a beam-maser spectrometer. The spectra show resolved splittings due to a different in molecular g-values for upper and lower inversion states with J = 3, K = 2. The observed difference in upper and lower inversion state g-values is g⁺(3,2)—g^?(3,2) = (1.38 ± 0.08) > 62;x 10^?4.     

Infrared band intensities: a comparative study of the transition moment matrix elements for the fundamental and overtones: Part II. Application to CO,HCl and OH

The various expressions considered in Part I for the transition moment matrix elements of fundamental and first two overtones are applied to carbon monoxide. The coefficients a_ij in the expressions R^io = Σa_ijp_j (where R^io is the transition moment integral for the O → i vibrational transition and p_j is the dipole moment derivative ?^jP/?XXX^j, XXX = (r — r_e)/r_e, r_e is equilibrium bond distance) are reported for i,j = 1, 2, 3. It is found that these coefficients do not vary by more than 5% when compared for the same i,j values in various expressions irrespective of the most exhaustive treatments used in deriving the original expressions. On the basis of the values of the coefficients obtained for CO, generalisations have been suggested on the effects of inclusion of mechanical and electrical anharmonicity to the intensities of fundamental and first two overtones. It is generally observed that the contribution of p'₁, is about 100 fold more than the contribution of p'₂, for R¹⁰. On the other hand the contributions of p'₁, and p, for R²⁰ and R³⁰ are of nearly equal magnitude but opposite in sign. The contribution of p'₁ to R¹⁰ is much higher than its contribution to R²⁰ and R²⁰. The various observations lead us to conclude that, whereas the effect of inclusion of mechanical anharmonicity on the intensity of the fundamental band is negligible, this effect is almost comparable to the effect of inclusion of electrical anharmonicity for the first two overtones. Simple forms of the a_ij expressions are applied to HC1 and OH to demonstrate the effect of variation of molecular constants on the a_ij values. On the basis of the observed trend in the values of these coefficients for CO, HCl and OH general remarks on the effects of hydrogen bonding on IR band intensities are given.     

Isomerization of Keggin Al13 Ions Followed by Diffusion Rates

The solution chemistry of aluminum has long interested scientists due to its relevance to materials chemistry and geochemistry. The dynamic behavior of large aluminum–oxo‐hydroxo clusters, specifically [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ ( Al₁₃ ), is the focus of this paper. ²⁷Al NMR, ¹H NMR, and ¹H DOSY techniques were used to follow the isomerization of the ?‐Al₁₃ in the presence of glycine and Ca²⁺ at 90 °C. Although the conversion of ?‐Al₁₃ to new clusters and/or Baker–Figgis–Keggin isomers has been studied previously, new ¹H NMR and ¹H DOSY analyses provided information about the role of glycine, the ligated intermediates, and the mechanism of isomerization. New ¹H NMR data suggest that glycine plays a critical role in the isomerization. Surprisingly, glycine does not bind to Al₃₀ clusters, which were previously proposed as an intermediate in the isomerization. Additionally, a highly symmetric tetrahedral signal (δ=72 ppm) appeared during the isomerization process, which evidence suggests corresponds to the long‐sought α‐Al₁₃ isomer in solution.     

Zum Aufbau schlecht geordneter Calciumhydrogensilicate. V 27AI-NMR-spektroskopische Untersuchungen zur Koordination des Al in C–S–H (Di,Poly)

On the Structure of Ill-crystallized Calcium Hydrogen Silicates. V. Studies on the Coordination of Al in C—S—H(Di, Poly) by ²⁷ Al-NMR Spectroscopy The coordination of aluminium incorporated into C—S—H(Di, Poly) (～0.07 Al₂O₃/SiO₂) [1] has been studied by high-resolution solid-state ²⁷ Al-NMR with magic angle spinning (MAS). It is shown that tetrahedrally as well as octahedrally coordinated Al occurs. With increasing CaO/SiO₂ ratio the amount of Al^[4] decreases, while that of Al^[6] increases. Specimens with 1 CaO/SiO₂ contain almost entirely Al—O tetrahedra and those with 1.5 CaO/SiO₂ only Al—O octahedra. Questions concerning the arrangement of Al in the lattice of C—S—H(Di, Poly) are discussed.     

Pulsed,Crossed, Supersonic Molecular Beam Studies of Refractory Atom Reactions

Dynamics of refractory atom reactions have been studied with a crossed beam apparatus combining two pulsed, supersonic molecular beam sources, a pulsed UV laser for creating the refractory atoms in the gas phase by laser ablation, and a pulsed dye laser to probe the reaction products by laser-induced fluorescence. Examples of the A1(²P_j) + O₂(X³∑_g)→ A10(X²∑⁺) + O(³P_j), Mg(¹S_o) + N₂O(X¹∑⁺) → MgO(X¹∑⁺,a³Π) + N₂(X¹∑_g⁺) andC(³P_j) + NO(X²Π_r) → CN(X²∑⁺) + 0(³P_j) systems are given. Comparisons with the studies performed using the conventional steady-state beam approach are made.     

Untersuchung der thermischen Zersetzung von Aluminium-dodekawolframatosilicat

Investigation on the Thermal Degradation of Aluminium-12-Tungstosilicate The dehydration of aluminium-12-tungstosilicate AlH[SiO₄W₁₂O₃₆] · 29 H₂O gives the anhydrous salt at 440°C. By means of X-ray heating patterns, thermal analysis, and i.r. spectroscopy the formation of the new phase 1/2 Al₂O₃ · SiO₂ · 12 WO₃ (I) at 500°C is observed, stable at room temperature. Above 800°C from I tetragonal W₃, Al₂(WO₄)₃, and amorphous SiO₂ are formed. Amorphous SiO₂ crystallizes to high-temperature cristobalite at 1000°C. High-resolution ²⁷Al NMR (MAS-technique) is used to determine the coordination number of aluminium in the different phases.     

Solid-state nuclear magnetic resonance investigation of synthetic phlogopite and lepidolite samples

In the present work, our aim is to decipher the cationic ordering in the octahedral and tetrahedral sheets of two Al-rich synthetic materials, namely, phlogopites of nominal composition K(Mg_3-xAl_x)[Al_1+xSi_3-xO₁₀](OH)_yF_2-y and lepidolites in the system trilithionite–polylithionite with composition K (Li_xAl_3-x)[Al_4-2xSi_2xO₁₀](OH)_yF_2-y, by directly probing the aluminium distribution through ²⁷Al and ¹⁷O magic-angle spinning, multiple-quantum magic-angle spinning, and ²⁷Al-²⁷Al double-quantum single-quantum nuclear magnetic resonance (NMR) experiments. Notably, ²⁷Al-²⁷Al double-quantum single-quantum magic-angle spinning NMR spectra, recorded at 9.34 and/or 20.00 T, show the spatial proximity or avoidance of the Al species inside or between the sheets. In both studied minerals, the ensemble of NMR data suggests a preference for ^[4]Al in the tetrahedral sheet to occupy position close to the ^[6]Al of the octahedral sheets.     

Activation of biscyclopentadienyl hydride complexes of titanium and aluminum by NH- and OH-acids in the reactions of hydrogenation of olefins. Crystal and molecular structures of {(η5−Cp)2Ti(μ−H)2AlH]μ−N(C2H4)4O]}2 and [(η5−Cp)2Ti(μ−H(2AlH]2(μ−OC2H4OMe)[(μ1:μ5−C5H4)Ti(μ5−Cp)(μ−H)]2*

The reactions of Cp₂TiH₂AlH₂·Et₂O (1) with HN(C₂H₄)₂O, HOC₂H₄OMe, and water afforded the complexes {Cp₂TiH₂AlH[μ-N(C₂H₄)₂O]}₂ (5), [Cp₂TiH₂AlH(μ-OC₂H₄OMe)]₂ (6) and (Cp₂TiH₂AlH)₂O (4), respectively. Compounds 5 and 6 are dimers containing bridging Al?E₂?Al fragments (E=N or O). Complex 6 in solution converted to the hexanuclear compound [(η⁵?Cp)₂Ti(μ?H(₂AlH]₂(μ?OC₂H₄OMe)[(μ¹:μ⁵?C₅H₄)Ti(μ⁵?Cp)(μ?H)]₂ (8). The structures of complexes 5 and 8 were established by X-ray diffraction analysis. The rates of hydrogenation of hex-1-ene were determined using compounds 4–6 and the complexes [Cp₂TiH₂AlH(NEt₂)]₂ and [Cp₂TiH₂AlH(OEt)]₂ as catalysts. The probable mechanism of hydrogenation with the participation of bimetallic hydride complexes of aluminum and titanocene is discussed.     

Effects of Mg,Al Co-doping into Mn site on electrochemical performance of LiNi<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript>

In order to study the influence of multiple ions doping into single-site on the structure and electrochemical properties of Ni-rich layered-structure cathode material LiNi_0.5Co_0.2Mn_0.3O₂, the coprecipitation of hydroxides was applied to synthesize Mg, Al co-doped cathode material LiNi_0.5Co_0.2Mn_0.3–x Mg_1/2x Al_1/2x O₂ (x = 0.00, 0.01, 0.02, 0.04) in this paper. Morphology and structure, kinetic parameter, impedance and electrochemical performance of the material were respectively characterized by SEM, XRD, CV, EIS and galvanostatic charge/discharge test. The results of comprehensive analysis showed that the properties of material were improved obviously when the amount of doping was 0.02. At this amount of doping, the corresponding material has smaller cation mixing, higher hexagonal ordering of layered-structure, larger Li⁺ ion diffusion coefficients which are 2.444 × 10^–10 and 4.186 × 10^–10 cm² s^–1 for Li+ intercalation and deintercalation respectively, smaller impedance which is 33.93 Ω, higher specific capacity of first-discharge which is 168.01 mA h g^–1 and higher capacity retention rate which is up to 95.06% after 20 cycles at 0.5 C (100 mA g^–1).     

Does He2 Exist?

For the electronic ground state X ¹Σ⁺_g, the potential-energy function of He₂ reported by Aziz et al. has been transformed into the form V(z), containing only eight parameters, which is more suitable for the investigation of the existence of states of discrete energy. We found no evidence that a bound vibration-rotational state of the stable diatomic molecule ³He₂ or ⁴He₂, even if rotating, can exist in the electronic ground state.     

Intensities of spin-forbidden transitions in molecular oxygen and selective heavy-atom effects

Intensities of a¹Δg←X ³∑_g^? and b ¹∑_g⁺ ← X ³∑_g^? transitions in molecular oxygen have been calculated on the basis of the INDO method taking into account spin-orbit coupling by perturbation theory. The transitions are magnetic dipole in nature. The first of them (a ? X) steals its intensity from ³Π_g-³∑_g^? and ¹Π_g-¹Δ_g transitions, which are determined by the orbital angular-momentum operator. This source is not the principal one for the intensity of the second (b-X) transition. Its intensity is stolen principally from microwave transitions between spin sublevels of the ground ³∑_g^? state. The last source explains the large difference in intensities of the a-X and b-X transitions. Calculated oscillator strengths are in a good agreement with experiment. The same integrals that determine the intensity also determine the parameters of the spin Hamiltonian for the ground ³∑_g^? state. These parameters are in a good agreement with experiment also, showing the validity of the whole calculation. In a condensed phase the investigated transitions are enhanced by intermolecular exchange interaction. It is known that an external heavy atom (EHA ) enhances the b-X transition of oxygen in solution, but does not influence the a-X transition. In the collision complex O₂-EHA , which has a geometry without inversion symmetry, the microwave transitions between spin sublevels of the “³∑_g^?” state obtain electric-dipole moments, which are stolen from the charge-transfer transition. This mechanism explains the selective effect of EHA .     

Analysis of the vibronic structure of the 1A1g → 1B3g, 1B2u transition in biphenyl -h10 and -d10

The absorption spectra of biphenyl-h₁₀ and -d₁₀ crystals in the region of the ¹A_1g → 1B_3g, ¹B_2u transitions are interpreted in terms of vibronic coupling of the two closely spaced electronic states by six b_1u vibrations.     

P2‐Na0.67AlxMn1−xO2: Cost‐Effective,Stable and High‐Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility

Sodium layered P2‐stacking Na_0.67MnO₂ materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn⁴⁺/Mn³⁺ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn³⁺, we obtain the low cost pure P2‐type Na_0.67Al_xMn_1?xO₂ (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na⁺ layer thus producing a remarkable rate capability of 96 mAh g^‐1 at 1200 mA g^‐1.     

Reaction of hydrogen atoms and O2(1Δg)

The reaction of atomic hydrogen with O₂(¹Δ_g) has been investigated as a function of temperature, using a fast discharge-flow apparatus equipped for EPR detection of free radical species. The rate constant for the overall reaction was measured as (1.46 ± 0.49) × 10^?11 exp(-4000 ± 200 cal/mol/RT) cm³/s. Evidence is presented which suggests that the reaction occurs principally via abstraction, H + O₂(¹Δ_g) → OH + O, rather than via physical quenching, H + O₂(¹Δ_g) → H + O₂(X³Σ_g^?).     

P2‐Na0.67AlxMn1−xO2: Cost‐Effective,Stable and High‐Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility

Sodium layered P2‐stacking Na_0.67MnO₂ materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn⁴⁺/Mn³⁺ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn³⁺, we obtain the low cost pure P2‐type Na_0.67Al_xMn_1?xO₂ (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na⁺ layer thus producing a remarkable rate capability of 96 mAh g^‐1 at 1200 mA g^‐1.     

Ruthenium(II/III) bipyridine complexes incorporating thiol-based imine functions: Synthesis,spectroscopic and redox properties

A group of five new ruthenium(II) bipyridine heterochelates of the type [Ru^II(bpy)₂L]⁺ 1a–1e have been synthesized (bpy=2,2′-bipyridine; L=anionic form of the thiol-based imine ligands, HS–C₆H₄NC(H)C₆H₄(R) (R=OMe, Me, H, Cl, NO₂). The complexes 1a−1e are 1:1 conducting and diamagnetic. The complexes 1a−1e exhibit strong MLCT transitions in the visible region and intra-ligand transitions in the UV region. In acetonitrile solvent complexes show a reversible ruthenium(III)–ruthenium(II) couple in the range 0.2–0.4 V and irreversible ruthenium(III)→ruthenium(IV) oxidation in the range 1.15–1.73 V vs. SCE. Two successive bipyridine reductions are observed in the ranges −1.43 to −1.57 and −1.67 to −1.78 V vs. SCE. The complexes are susceptible to undergo stereoretentive oxidations to the trivalent ruthenium(III) congeners. The isolated one-electron paramagnetic ruthenium(III) complex, 1c⁺ exhibits weak rhombic EPR spectrum at 77 K (g₁=2.106, g₂=2.093, g₃=1.966) in 1:1 chloroform–toluene. The EPR spectrum of 1c⁺ has been analyzed to furnish values of distortion parameters (Δ=8988 cm⁻¹; V=0.8833 cm⁻¹) and energy of the expected ligand field transitions (ν₁=1028 nm and ν₂=1186 nm) within the t₂ shell. One of the ligand field transitions has been experimentally observed at 1265 nm.     

Der chemische Transport von CrCl3,f mit Al2Cl6,g über die Gasmolekel CrCl3·3 AlCl3

CrCl₃,_g is chemically transported by means of Al₂Cl_6,g (～1 atm) in a temperature gradient (e. g. 500 → 400°C). Quantitative transport experiments have shown that the reaction goes via the gas molecule CrCl₃ · 3 AlCl₃. Its probable structural formula is CrCl_6/2(AlCl_2/2Cl₂)₃, containing Cr³⁺ in an octahedral and Al³⁺ in a tetrahedral Cl coordination¹).