A study of the reaction O + CS2 → SO + CS using crossed molecular beams

Measurements of SO scattering from the reaction O + CS₂ → SO + CS using crossed thermal molecular beams show that (a) there is strong forward sca     

Vibrational excitation following the Sls core ionization of CS

Ab initio non-relativistic spin-unrestricted Hartree-Fock calculations are performed on CS and its Sls core-ionized state. Geometrical relaxation is investigated. As in the corresponding first-row CO, relaxation greatly influences the vibrational band profile. The one-particle vibrational picture leads to bond-length shortening whereas relaxation and direct calculations indicate a slight bond-length increase, leading to a predicted small vibrational broadening.     

Measurements of the bimolecular rate constants for S + O2 → SO + O and CS2 + O2 → CS + SO2 at high temperatures

The bimolecular reactions in the title were measured behind shock waves by monitoring the O-atom production in COS? O₂? Ar and CS₂? O₂? Ar mixtures over the temperature range between 1400 and 2200 K. A value of the rate constant for S + O₂ → SO + O was evaluated to be (3.8 ± 0.7) × 10¹² cm³ mol^?1 s^?1 between 1900 and 2200 K. This was connected with the data at lower temperatures to give an expression k₂ = 10^10.85 T^0.52 cm³ mol^?1 s^?1 between 250 and 2200 K. An expression of the rate constant for CS₂ + O₂ → CS + SO₂ was obtained to be k₂₁ = 10^12.0 exp(?32 kcal mol^?1/RT) cm³ mol^?1 s^?1 with an error factor of 2 between 1500 and 2100 K.     

Theoretical analysis of the O + CS(0) → CO(υ′)+ S reaction by the two half-collisions model

A theoretical analysis of the O + CS → CO + S reaction is presented. It is shown that the experimental CO vibrational distribution can be explained by a collinear O + CS reaction which proceeds via the lowest triplet OCS electronic state.     

A chemically pumped CO2 laser from the CS2O2 reaction

A chemical laser has been constructed in which simultaneous output is obtained from both CO and CO₂ laser species at 5 and 10 μm, respectively. Excitation of CO₂ is via energy transfer from vibrationally excited CO (CO²) produced in the photolytically initiated reaction: O + CS → CO² + S. Gain measurements at the CO₂ laser frequencies are also reported.     

A comment on the vibrational distribution of CO produced by the reaction of O with CS and CS2

There have been several meaurements of the CO vibrational distribution fromthe reaction of O with CS; these distributions differ significantly for vibrational levels below μ = 6. The differences can be reconciled by considering, via surprisal analysis techniques, the contribution of CO production from O + CS₂.     

Laser-induced fluorescence measurement of the vibrational distribution of CS formed in the reaction O + CS2 → CS + So

A frequency-doubled cw dye laser has been used to determine the initial vibrational distribution of CS formed in the reaction O + CS₂ → CS + SO by application of laser-induced fluorescence. The A¹5—X¹σ⁺ system of CS was excited, and rotationally resolved spectra of a number of bands measured. The vibrational distribution found for υ = 0–2 is 1.0:0.27:0.11, yielding a value of 6% for the fraction of reaction exoergicity entering vibration of this product. No evidence of high product rotational excitation wss detected for a reaction pressure 5 × 10^?3 Torr.     

Vibrational mode and collision energy effects on reaction of H2CO+ with CO2

The effects of collision energy (Ecol) and five different modes of H2CO+ vibration on the title reaction have been studied over the center-of-mass Ecol range from 0.1 to 3.2 eV, including measurements of product ion recoil velocity distributions. Electronic structure and Rice-Ramsperger-Kassel-Marcus calculations were used to examine properties of various complexes and transition states that might be important along the reaction coordinate. Two product channels are observed, corresponding to Hydrogen Transfer (HT) and Proton Transfer (PT). Both channels are endothermic with similar onset energies of approximately 0.9 eV; however, HT dominates over the entire Ecol range and accounts for 70-85% of the total reaction cross section. Both HT and PT occur by direct mechanisms over the entire Ecol range, and have similar dependence on reactant vibrational and collision energy. Despite these similarities, and the fact that the two channels are nearly isoenergetic and differ only in which product moiety carries the charge, their dynamics appear quite different. PT occurs primarily in large impact parameter stripping collisions, where most of the available energy is partitioned to product recoil. HT, in contrast, results in internally hot products with little recoil energy and a more forward-backward symmetric product velocity distribution. Vibration is found to affect the reaction differently in different collision energy regimes. The appearance thresholds are found to depend only on total energy, i.e., all modes of vibration are equivalent to Ecol. With increasing Ecol, vibrational energy becomes increasingly effective, relative to Ecol, at driving reaction. For HT, this transition occurs just above threshold, while for PT it begins at roughly twice the threshold energy.     

CS2O+ and CS2O in the gas phase: an experimental and computational study

The CS2O+ ion and CS2O molecule were prepared and structurally characterized by mass spectrometric techniques as isolated species in the gas phase. The theoretical analysis, performed by B3LYP and CCSD(T) computational methods, predicted different CS2O+ isomers, SSCO+, O(CS2)+, SCSO+, SCOS+ and S(COS)+, and structurally related singlet and triplet CS2O. Experiment and theory agree in identifying the obtained CS2O+ ions as a mixture of SCSO+ and SCOS+ isomers. CS2O neutral species, prepared by neutralization-reionization mass spectrometry, were directly characterized as intact, long-lived species with a lifetime tau > or =2 micros.     

Rate constant and products of the reaction CS2 + OH in the presence of O2

The reaction of OH radicals with CS₂ has been investigated by the application of Fourier transform infrared spectroscopy using both photolytic and nonphotolytic competitive techniques in a 420-L reaction chamber at different pressures over the temperature range of 264–293 K. The measured effective rate constant was found to be dependent on total pressure, temperature, and the mole fraction of O₂ present in the system. The products of the reaction were found to be COS and SO₂ with one molecule of each being formed for every reacted CS₂. A value of (2.7 ± 0.6) × 10^?12 cm³/molecule·s was obtained as effective rate constant for the reaction at 293 K in 760 torr of synthetic air.     

Vibrational population distribution of ground state BaO formed by the reaction Ba + O2

The vibrational population distribution of X ¹Σ(υ′' = 0 through ν′' = 7) BaO formed in the reaction Ba + O₂ at 0.3 torr has been measured by laser induced photoluminescence intensities. On the basis of the assumed similarity between the Ba + O₂ and Ba + N₂O reactions, these data suggest that a population inversion may exist between A ¹Σ(ν′ = 1) and X ¹Σ(υⁿ = 7) BaO formed in the latter reaction at ≈ 16 torr.     

Mechanistic and kinetic study of the CH3CO + O2 reaction

Potential-energy surface of the CH3CO + O2 reaction has been calculated by ab initio quantum chemistry methods. The geometries were optimized using the second-order Moller-Plesset theory (MP2) with the 6-311G(d,p) basis set and the coupled-cluster theory with single and double excitations (CCSD) with the correlation consistent polarized valence double zeta (cc-pVDZ) basis set. The relative energies were calculated using the Gaussian-3 second-order Moller-Plesset theory with the CCSD/cc-pVDZ geometries. Multireference self-consistent-field and MP2 methods were also employed using the 6-311G(d,p) and 6-311++G(3df,2p) basis sets. Both addition/elimination and direct abstraction mechanisms have been investigated. It was revealed that acetylperoxy radical [CH3C(O)OO] is the initial adduct and the formation of OH and alpha-lactone [CH2CO2(1A')] is the only energetically accessible decomposition channel. The other channels, e.g., abstraction, HO2 + CH2CO, O + CH3CO2, CO + CH3O2, and CO2 + CH3O, are negligible. Multichannel Rice-Ramsperger-Kassel-Marcus theory and transition state theory (E-resolved) were employed to calculate the overall and individual rate coefficients and the temperature and pressure dependences. Fairly good agreement between theory and experiments has been obtained without any adjustable parameters. It was concluded that at pressures below 3 Torr, OH and CH2CO2(1A') are the major nascent products of the oxidation of acetyl radicals, although CH2CO2(1A') might either undergo unimolecular decomposition to form the final products of CH2O + CO or react with OH and Cl to generate H2O and HCl. The acetylperoxy radicals formed by collisional stabilization are the major products at the elevated pressures. In atmosphere, the yield of acetylperoxy is nearly unity and the contribution of OH is only marginal.     

Reaction Mechanism Investigation Using Vibrational Mode Anal—ysis for the Multichannel Reacition of CH3O＋CO

On the basis of the computed results got by the Gaussian 94 package at B3LYP/6-311 G** level,the reaction mechanism of CH3O radical with CO has been investiagted thoroughly via the vibrational model analysis ,And the relationships among the reactants,eight transition states,four intermediates and various products involved this multichannel reation are eluci-dated,The vibrational mode anaysis shows that the reaction mechanism is relialbe.     

Reaction Mechanism Investigation Using Vibrational Mode Analysis for the Multichannel Reaction of CH_3O+CO

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Ca+催化的N2O+CO反应机理的理论研究

采用B3LYP/cc-pVTZ理论水平系统研究了Ca+离子催化N2O+CO→N2+CO2反应的微观机理.反应分两步进行:第一步Ca+夺取N2O中的O原子有两条反应通道,其中优势通道为Ca+金属离子与N2O分子中O作用,形成线性分子复合物,活化N2O分子中的N-O键,之后的反应路径为O-N键断裂机理;第二步为CaO+金属...     

Quantum chemical and theoretical kinetics study of the O(3P) + CS2 reaction

The triplet potential energy surface of the O((3)P) + CS(2) reaction is investigated by using various quantum chemical methods including CCSD(T), QCISD(T), CCSD, QCISD, G3B3, MPWB1K, BB1K, MP2, and B3LYP. The thermal rate coefficients for the formation of three major products, CS + SO ((3)Σ(-)), OCS + S ((3)P) and CO + S(2) ((3)Σ(-)(g)) were computed by using transition state and RRKM statistical rate theories over the temperature range of 200-2000 K. The computed k(SO + CS) by using high-level quantum chemical methods is in accordance with the available experimental data. The calculated rate coefficients for the formation of OCS + S ((3)P) and CO + S(2) ((3)Σ(-)(g)) are much lower than k(SO + CS); hence, it is predicted that these two product channels do not contribute significantly to the overall rate coefficient.     

Vibrational excitation effects on silane reactivity in its reaction with bromine atoms

A rate increase of SiH₃Br formation in SiH₄ photobromination under irradiation by a cw CO₂ laser is reported. At low SiH₄ pressures (1–2 Pa) the radiation effect is shown to be isotope-selective.

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SiH₃Br CO₂ SiH₄. , SiH₄ (1–2 ) .

     

Angular momentum conservation in the O + OH ↔ O2 + H reaction

We have studied the O + OH ↔ O₂ + H reaction on Varandas's DMBE IV potential using a variety of statistical methods, all involving the RRKM assumption for the HO₂* complex. Comparing our results using microcanonical variational transition‐state theory (μVT) with those using microcanonical/fixed‐J variational transition‐state theory (μVT‐J), we find that the effect of angular momentum conservation on the rate coefficient is imperceptible up to a temperature of about 700 K. Above 700 K angular momentum conservation increasingly reduces the rate coefficient, but only by approximately 21% even at 5000 K. Comparing our μVT‐J calculations with the quasi‐classical trajectory (QCT) results of Miller and Garrett [ 1 ], we confirm their conclusion that non‐RRKM dynamics of the HO₂* complex reduces the rate coefficient by about a factor of 2 independent of temperature. Our calculations of k^(c), the rate coefficient for HO₂* formation from O + OH, are in excellent agreement with the QCT results of Miller and Garrett. Although the differences are not large, we find k_CVT^(c) > k_μVT^(c) > k_μVT‐J^(c) > k_QCT^(c), where CVT stands for canonical variational transition‐state theory. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 753–756, 1999     

Vibrational excitation of OH(X2Π) produced in the reaction of O(1D) with H2

A lower limit to the OH(X²Π) vibrational excitation produced by the reaction O(¹D) + H₂ has been observed using a low-pressure infrared chemiluminescence apparatus. The O(¹D) was generated by laser photolysis of O₃. The measured OH(v') vibrational distribution is inverted; it peaks at v' = 2.