Adiabatic calculations of the 2Σ+g excited states of He+2

The first six ²Σ⁺_g adiabatic potential energy curves of He⁺₂ are calculated with the MRD CI method employing configuration selection (T = 10 μ hartree) and perturbative energy corrections and using two basis sets differing in the number of diffuse functions. The non-adiabatic matrix elements at the numerous avoided crossings are also calculated and approximate diabatic curves are constructed. Various aspects of the results are discussed.     

Mean potential statistical theory of the H+ + D2 → HD + D+ reaction

The reactive collision process H(+) + D(2)(ν = 0, j = 0) → HD + D(+) is theoretically analyzed for collision energies ranging from threshold up to 1.3 eV. It is assumed that the reaction takes place via formation of a collision complex. In calculations, a statistical theory is used, based on a mean isotropic potential deduced from a full potential energy surface. Calculated integral cross sections, opacity functions, and rotational distributions of the HD products are compared with recent statistical and quantum mechanical calculations performed using a full potential energy surface. Satisfactory agreement between the results obtained using the two statistical methods is found, both of which however overestimate the existing quantum mechanical predictions. The effects due to the presence of identical particles are also discussed.     

Determination of the Rate Constants of the Reactions Cr + O2 + M → CrO2 + M and Cr + O2 → CrO + O

Kinetics and Catalysis - The rate constants of the interactions of chromium atoms with molecular oxygen through recombination Cr + O2 + M → CrO2 + M (I) and exchange Cr + O2 → CrO + O...     

Quasi-classical trajectory studies of the stereodynamics of the reaction O + HCl → ClO + H

The stereodynamics of the O + HCl → ClO + H reaction are investigated by quasi-classical trajectory (QCT) method. The calculations are carried out on the ground 1 ¹ A′ potential energy surface (PES). The orientation and alignments of the product rotational angular momentum for the title reaction are reported. The influence of collision energy on the product vector properties is also studied in the present work. Four (2π/σ)(dσ₀₀/dω _t ), (2π/σ)(dσ₂₀/dω _t ), (2π/σ)(dσ₂₂₊/dω _t ), and (2π / σ)(dσ₂₁₋/dω _t ), and have been calculated in the center of mass frame.     

Analysis of the long range potentials of the X 1Σ+ and a 3Σ+ states of NaK

The difference in energy between the singlet and triplet states of NaK dissociating to Na(3s) and K(4s) is found from experimental data and from pseudopotential calculations. The contributions of various one- and two-electron integrals are evaluated, illustrating the present ambiguity over the exchange integral and the exchange interaction terms.     

Acceleration of the reaction OH + CO → H + CO2 by vibrational excitation of OH

The collision complex formed from a vibrationally excited reactant undergoes redissociation to the reactant, intramolecular vibrational relaxation (randomization of vibrational energy), or chemical reaction to the products. If attractive interaction between the reactants is large, efficient vibrational relaxation in the complex prevents redissociation to the reactants with the initial vibrational energy, and the complex decomposes to the reactants with low vibrational energy or converts to the products. In this paper, we have studied the branching ratios between the intramolecular vibrational relaxation and chemical reaction of an adduct HO(v)-CO formed from OH(X(2)Π(i)) in different vibrational levels v = 0-4 and CO. OH(v = 0-4) generated in a gaseous mixture of O(3)/H(2)/CO/He irradiated at 266 nm was detected with laser-induced fluorescence (LIF) via the A(2)Σ(+)-X(2)Π(i) transition, and H atoms were probed by the two-photon excited LIF technique. From the kinetic analysis of the time-resolved LIF intensities of OH(v) and H, we have found that the intramolecular vibrational relaxation is mainly governed by a single quantum change, HO(v)-CO → HO(v-1)-CO, followed by redissociation to OH(v-1) and CO. With the vibrational quantum number v, chemical process from the adduct to H + CO(2) is accelerated, and vibrational relaxation is decelerated. The countertrend is elucidated by the competition between chemical reaction and vibrational relaxation in the adduct HOCO.     

Properties of DNA + Dipropylsulfoxide or Dibutylsulfoxide + Water Ternary Solutions

Aqueous solutions of DNA in the presence of dipropylsulfoxide (DPSO) and of dibutylsulfoxide (DBSO) have been studied using UV-vis spectroscopy and density measurements. It has been shown that significant thermal denaturation of DNA occurs when DPSO or DBSO are present. The results obtained were compared with those obtained previously with dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO). It is suggested that the lowering of the transition enthalpy with increasing length of the carbon chain of the dialkylsulfoxides is due to significance contribution from hydrophobic interactions.     

Quasi-classical Trajectory Study of Ba+HI→BaI+H Reaction

The quasi-classical trajectory calculations based on extended London-Eyring-Polanyi-Sato potential energy surface have been used to study the reaction of Ba+HI→BaI+H system. The rotational, vibrational, translational, and angular distributions of the product BaI have been calculated. The calculated results are in good agreement with the experimental ones.     

Fluid phase topology of ethanol+benzene+cyclohexane at 101.3 kPa

In this article, isobaric vapor–liquid equilibria for the ternary mixture of ethanol?+?benzene?+?cyclohexane was experimentally investigated at atmospheric pressure. Vapor–liquid equilibria data for ethanol?+?benzene?+?cyclohexane at 101.3?kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits three binary homogeneous azeotropes and a ternary minimum azeotrope at the studied conditions. Satisfactory results were obtained for correlation of equilibrium compositions with UNIQUAC activity coefficients model and also for prediction with UNIFAC method. In both cases, low root mean square deviations of vapor mole fraction and temperature were calculated. The capability of ethanol as modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. However, owing to the complex topology of the ternary mixture it leads to a distillation scheme with three columns and difficult operation and thus, ethanol is not recommended as a separating agent for benzene?+?cyclohexane azeotrope.     

Quantum dynamics of the S+OH→SO+H reaction

First accurate quantum mechanical scattering calculations have been carried out for the S((3)P)+OH(X?(2)Π)→SO(X?(3)Σ(-))+H((2)S) reaction using a recent ab initio potential energy surface for the ground electronic state, X?(2)A("), of HSO. Total and state-to-state reaction probabilities for a total angular momentum J=0 have been determined for collision energies up to 0.5 eV. A rate constant has been calculated by means of the J-shifting approach in the 10-400 K temperature range. Vibrational and rotational product distributions show no specific behavior and are consistent with a mixture of direct and indirect reaction mechanisms.     

Ab Initio Study on the Reaction of La~+ + CH_4→La+-CH~2 + H_2

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Quasi-classical trajectory study of the dynamics of the Cl + CH4→ HCl + CH3 reaction

We present an on-the-fly classical trajectory study of the Cl + CH(4)→ HCl + CH(3) reaction using a specific reaction parameter (SRP) AM1 Hamiltonian that was previously optimized for the Cl + ethane reaction [S. J. Greaves et al., J. Phys Chem A, 2008, 112, 9387]. The SRP-AM1 Hamiltonian is shown to be a good model for the potential energy surface of the title reaction. Calculated differential cross sections, obtained from trajectories propagated with the SRP-AM1 Hamiltonian compare favourably with experimental results for this system. Analysis of the vibrational modes of the methyl radical shows different scattering distributions for ground and vibrationally excited products.     

Liquid–liquid phase equilibrium of methanol + ethylbenzene + isooctane + ethanol system at 303 K

The phase equilibrium data for methanol + ethanol + isooctane systems were obtained at 303.15 K. Data for methanol + ethylbenzene + isooctane system were taken from literature. The effect of ethanol addition on the system equilibrium was investigated at the same temperature. The distribution curves for ternary and quaternary system was analyzed. The experimental results for ternary systems were correlated with UNIQUAC and NRTL equations. For the ternary systems studied here, the NRTL equation is more accurate than the UNIQUAC. The equilibrium data for the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. For the quaternary system, the experimental data can be fitted more accurately to UNIQUAC equation than by the UNIFAC method.     

Dynamics and mode-selected reaction of NCO+H_2→HNCO+H

The reaction path of the reaction NCO+H2→HNCO + H has been traced by Fukui's theory and the ab initio method. On this basis, the dynamical properties along the reaction path, canonical variational theory (CVT) rate constants and vibrational-mode-selected rate constants have been computed. The results show that the effect of the electron correlation energy on the activation barrier is large, and tiros the correction by MP4 method is effective; the results also show that the recrossing and tunneling effects exist, and thus the corrections by the variational transition state theory (VTST) and the small curvature (SC) approximation method are also effective. In the reaction, the coupling and energy transfer between mode 8(7) and reaction path are strong, so the rate is effectively enhanced while these modes, especially H2 stretching, are vibrationally excited.     

Kinetics and thermochemistry of [2π + 2σ + 2σ]-cycloaddition of quadricyclane to tetracyanoethylene

Kinetic data for the unusual [2π + 2σ + 2σ]-cycloaddition of quadricyclane to tetracyanoethylene in toluene have been obtained for the first time. The same reaction in 1,4-dioxane appears to be the most exothermic among known cycloaddition reactions. The entropy of activation and reaction volume differ only slightly from the corresponding parameters of conventional Diels–Alder reactions.     

Effect of Reagent Rotational Excitation on Dynamics of F+H2→HF+H

The dynamics of the F+H₂(v=0,j=0, 1) reactions have been studied at the collision energy of 1.27 kcal/mol using a high-resolution crossed molecular beam apparatus. HF product rotational state resolved differential cross sections have been obtained at the v′=1, 2, 3 levels. The product HF(v′=2) angular distributions are predominantly backward scattered for both H₂ (j=0, 1) reagents. However, the distributions of product HF(v′=2) rotational states for theF+H₂(v=0,j=0) reaction are signi cantly di erent from those for the F+H₂(v=0,j=1) reaction. Experimental results show that the rotational excitation of H₂ produces rotationally ‘hotter’ HF(v′=2) product. In addition, the HF(v′=3) product is more likely scattered into the forward direction when the H₂ reagent is populated at j=0 state, which could be attributed to a slow-down mechanism.     

Relativistic calculations of AuSi+ and AuSi−

Theoretical calculations of the electronic structure of the ground state and a series of excited states of the AuSi⁺ and AuSi⁻ molecules are presented. The calculations were carried out with the spin-free relativistic infinite-order two-component (IOTC) method and high-level complete active space self-consistent field/complete active space perturbation theory correlated methods. The spin-orbit (SO) coupling was introduced via the restricted active space state interaction method with the use of the atomic mean-field SO integrals. The work presents the spectroscopic parameters of calculated states and full potential energy curves of the ionic AuSi⁺ and AuSi⁻ structures for the first time. Electrostatic potential maps projected on the electron density surface illustrate the significant relativistic effects on going from nonrelativistic to scalar relativistic treatments.     

Study of the ν2 + ν3 infrared band of ONCl

Two hundred and sixty A type rovibrational lines of the ν₂ + ν₃ vibrational band of ¹⁶O¹⁴N³⁵Cl, around 925 cm⁻¹, have been assigned; a least-squares calculation with a r.m.s. deviation of 0.0006 cm⁻¹ has made it possible to measure several constants of the (011) vibrational level.     

Fitting of the voltage–Li+ insertion curve of LiFePO4

Fitting of the voltage vs. insertion curves of the LiFePO₄ electrode was based on theoretical expressions describing the Li⁺ diffusive process in a solid medium. The noninteracting gas model for the chemical potential of ions distributed in a solid matrix was taken into account, and the diffusion coefficient and the energy activation for the diffusion process were accordingly calculated. The polarization curves at various discharge stages were theoretically obtained, and a good agreement was found with the experimental data at all discharge rates. A mathematical relation describing the trend of the diffusion resistance vs. insertion degree was also developed.