Electron transfer and bond-forming reactions following collisions of Cl2+ and HCl2+ with CO

Collisions between Cl(2+) and CO have been investigated using time-of-flight mass spectrometry over a collision energy range between 2.2 eV and 7.1 eV in the centre-of-mass frame. The formation of Cl(+), CO(+) and C(+) in electron transfer reactions has been detected and an unusual bond-forming reaction which generates CCl(2+) has also been observed. The reactive cross-sections, in arbitrary units, for the electron transfer reactions have been evaluated. To extract these cross sections we employ a new method of analysing mass spectral intensities for crossed-beam experiments, an algorithm which allows inter-comparison of the fluxes of all the ionic products from the electron transfer reactions. The observed electron transfer reactivity has been rationalized by calculations based on Landau-Zener theory. To account for the observation of CCl(2+), we have calculated the relevant energetics showing that the lowest lying doublet state of this dication is bound and is energetically accessible at our collision energies. These energetic arguments indicate that electron transfer in the exit channel between the separating CCl(2+) and O atom probably forms C(+) ions via the dissociation of CCl(+). Additionally, collisions between HCl(2+) and CO have been studied at collision energies from 2.2 to 7.0 eV in the centre-of-mass frame. In this collision system, proton transfer to form HCO(+) is observed to compete efficiently with dissociative and non-dissociative electron transfer.     

Local angular momentum-local impact parameter analysis: derivation and properties of the fundamental identity, with applications to the F+H2, H+D2, and Cl+HCl chemical reactions

The technique of local angular momentum-local impact parameter (LAM-LIP) analysis has recently been shown to provide valuable dynamical information on the angular scattering of chemical reactions under semiclassical conditions. The LAM-LIP technique exploits a nearside-farside (NF) decomposition of the scattering amplitude, which is assumed to be a Legendre partial wave series. In this paper, we derive the "fundamental NF LAM identity," which relates the full LAM to the NF LAMs (there is a similar identity for the LIP case). Two derivations are presented. The first uses complex variable techniques, while the second exploits an analogy between the motion of the scattering amplitude in the Argand plane with changing angle and the classical mechanical motion of a particle in a plane with changing time. Alternative forms of the fundamental LAM-LIP identity are described, one of which gives rise to a CLAM-CLIP plot, where CLAM denotes (Cross section) x LAM and CLIP denotes (Cross section) x LIP. Applications of the NF LAM theory, together with CLAM plots, are reported for state-to-state transitions of the benchmark reactions F+H2-->FH+H, H+D2-->HD+D, and Cl+HCl-->ClH+Cl, using as input both numerical and parametrized scattering matrix elements. We use the fundamental LAM identity to explain the important empirical observation that a NF cross section analysis and a NF LAM analysis provide consistent (and complementary) information on the dynamics of chemical reactions.     

The state-to-state-to-state model for direct chemical reactions: application to D+H2-->HD+H

A simple theoretical model is developed to predict the state-to-state dynamics of direct chemical reactions. Motivated by traditional ideas from transition state theory, expressions are derived for the reactive S matrix that may be computed using the local transition state dynamics. The key approximation involves the use of quantum bottleneck states to represent the near separable dynamics taking place near the transition state. Explicit expressions for the S matrix are obtained using a Franck-Condon treatment for the inelastic coupling between internal states of the collision complex. It is demonstrated that the energetic thresholds for various initial reagent states of the D+H(2) reaction can be understood in terms of our theory. Specifically, the helicity of the reagent states are found to correlate directly to the symmetry of the quantum bottleneck states, which thus possess very different thresholds. Furthermore, the rotational product state distributions for D+H(2) are found to be associated with interfering pathways through the quantum bottleneck states.     

Gas phase reactions of SiF2 with F2 and Cl2

Reactions of SiF₂ radicals have been studied in a fast-flow system. Rate constants at 295 K of (4.7±0.3)×10⁻¹³ cm³ molecule⁻¹ s⁻¹ for the reaction of SiF₂ + F₂, and (5.1±0.6)×10⁻¹³ cm³ molecule⁻¹ s⁻¹ for SiF₂ + Cl₂ were obtained. No reaction was observed with O₂ and H₂. SiF₂ was detected by laser-induced fluorescence, and lifetime observations and an excitation spectrum are reported.     

The microscopic reaction dynamics and branching ratio in the F + HCOOH and F + H2CO reactions

Infrared chemiluminescence under conditions of arrested relaxation has been applied to the study of the hydrogen and deuterium abstraction reactions of HCOOH, DCOOH and H₂CO with F atoms. Two distinctly different modes of product excitation are observed, depending upon whether the reaction proceeds via the formyl or carboxyl hydrogen. Reaction at the formyl hydrogen (or deuterium) causes substantial inversion in the diatomic product internal energy distributions. The F + H₂CO and F + DCOOH reactions respectively channel 56% and 54% of the available energy into vibration in the product diatomic when they occur at the formyl site. In both cases the product energy distributions are qualitatively similar to those observed in direct reactions of triatomic systems on repulsive energy surfaces. In contrast to these, reaction at the carboxyl hydrogen of DCOOH gives an HF2 product vibrational distribution having a Boltzmann equilibrium shape at a temperature of 4300 K. The ratio of HF to DF product from the F + DCOOH study shows that reaction occurs at the carboxyl hydrogen approximately twice as often as at the formyl site. Comparison with triatomic reactions involving the same mass-combinations implies that abstraction of the formyl hydrogen occurs via single-collision, direct encounters, whereas reaction at the carboxyl site involves a long-lived complex in which extensive randomisation of the reaction exoergicity among all the product vibrational modes can occur.     

A simple chemosensor for Hg2+ and Cu2+ that works as a molecular keypad lock

A new chemosensor which can detect Hg(2+) in water and Hg(2+)/Cu(2+) in acetonitrile and its application as a molecular keypad lock using Cu(2+) and F(-) as ionic inputs are demonstrated.     

Infrared chemiluminescence from the reactions F + HBr,F + H2Se,and Cl + H2Se

Infrared chemiluminescence from HF and HCl has been observed and yielded vibrational and rotational population distributions for the reactions F + HBr, F + H₂Se, and Cl + H₂Se. Evaluation of the spectra recorded by a commercial Fourier-transform spectrometer under low-flow conditions gave the following relative vibrational populations: for F ? HBr. N_{υ = 1} : N_{υ = 2} : N_{υ = 3} : N_{υ = 4} = 0.45 : 0.31 : 0.13 : 0.11: for F + H₂Se, N_{υ = 1} : N_{υ = 2} : N_{υ = 3} : N_{υ = 4} : N_{υ = 5} = 0.29 : 0.35 : 0.24 : 0.09 : 0.03: for Cl + H₂Se, N_{υ = 1} : N_{υ = 2} : N_{υ = 3} = 0.40 : 0.51 : 0.09. All three vibrational surprisal plots show a significant deviation from linearity. Neglecting the contributions from N_{υ = 0}, the total energy is partitioned into vibration and rotation as follows: 〈f_V〉 = 0.49 and 〈f_R〉 = 0.09 for F + HBr, 〈f_V〉 = 0.41 and 〈f_R〉 = 0.07 for F + H₂Se, 〈f_V〉 = 0.53 and 〈f_R〉 = 0.10 for Cl + H₂Se. Inclusion of estimates for N_{υ = 0} gives the more realistic values 〈f_V〉 = 0.24, 0.34, and 0.49 respectively. Whereas 9 ± 3% of the collisions between F + HBr yield Br in the excited ²P_{$\text{1}\text{2}$} state, no rovibrationally excited HSe fragments were detected in the two other systems. Consistent values for the bond dissociation energy D₀⁰(HSeH) = 329 ± 5 kJ/mol and the enthalpy of formation ΔH₁₀⁰ (HSe) = 137 ± 5 kJ/mol are derived from the highest observed HCl and HF levels.     

氯分子束与钛表面激光化学反应动力学

本文采用飞行时间质谱技术测定了在紫外(355nm), 可见(560nm)和近代红外(1064nm)脉冲激光作用下, 氯分子束与Ti表面反应产物的质量分布和速度分布。所得结果表明, 不同波长激光诱导反应的主要产物相同, 有Ti, TiCl, TiCl3和TiCl4。在高能量密度的紫外激光作用下, 首次测得具有很高动能的原生Ti+。各种含Ti氯化物的飞行时间谱, 能满意地用单组分或多组分Maxwell-Boltzmann公式拟合和分析。上述激光诱导气-固表面反应的机理主要由氯分子在Ti表面上的解离吸附,吸附态氯原子在表面上生成TiClx(X=1～4)的连串反应以及激光诱导脱附所组成。近红外激光主要引起热脱附, 而紫外激光的作用还原可能有非热脱附过程。     

The determination of the arrhenius parameters for the reaction Cl + C2F5I → ICl + C2F5 using a competitive method

The reactions have been studied competitively over the range of 28–182°C by photolysis of mixtures of Cl₂ + C₂F₅I+ CH₄. We obtain where θ = 2.303RT J/mol. The use of published data on reaction (2) leads to log (k₁cm³/mol sec) = (13.96 ± 0.2) ? (11,500 ± 2000)/θ.     

Quantum approaches for the insertion dynamics of the H+ + D2 and D+ + H2 reactive collisions

The H(+)+D(2) and D(+)+H(2) reactive collisions are studied using a recently proposed adiabatic potential energy surface of spectroscopic accuracy. The dynamics is studied using an exact wave packet method on the adiabatic surface at energies below the curve crossing occurring at approximately 1.5 eV above the threshold. It is found that the reaction is very well described by a statistical quantum method for a zero total angular momentum (J) as compared with the exact ones, while for higher J some discrepancies are found. For J >0 different centrifugal sudden approximations are proposed and compared with the exact and statistical quantum treatments. The usual centrifugal sudden approach fails by considering too high reaction barriers and too low reaction probabilities. A new statistically modified centrifugal sudden approach is considered which corrects these two failures to a rather good extent. It is also found that an adiabatic approximation for the helicities provides results in very good agreement with the statistical method, placing the reaction barrier properly. However, both statistical and adiabatic centrifugal treatments overestimate the reaction probabilities. The reaction cross sections thus obtained with the new approaches are in rather good agreement with the exact results. In spite of these deficiencies, the quantum statistical method is well adapted for describing the insertion dynamics, and it is then used to evaluate the differential cross sections.     

Analytical energy surfaces for the collinear H+H2 and Li+H2 exchange reactions

A simple four-parameter function is shown to possess adequate flexibility to fit the H + H₂ →H₂ + H and Li + H₂ → LiH + H exchange reaction energy surfaces to good accuracy along the reaction paths.     

Investigations with the finite element method. II. The collinear F + H2 reaction

We are investigating systematically the use of the finite element method (FEM) for solving the Schrödinger equation. The present work is devoted to the calculation of vibrational transition probabilities for the collinear reactive system F + H₂. The calculations are fully two-dimensional and the results are compared with the conventional basis set expansion methods using the R-matrix or S-matrix propagation. Extensive analysis of FEM on the vector computer Cyber 205 was made and a vector code for the efficient use in two dimensions was developed, so that in the near future applications even in three dimensions will be possible. The details of our FEM calculations are the following: The integration area was discretized into triangles where quadratic polynomials for the local wavefunction were defined. Convergent results can be reached with this simple ansatz with roughly 10000 grid points.     

Potential energy surfaces for simple chemical reactions: Li + F2 → LiF + F

A potential energy surface is calculated for the Li + F₂ → LiF + F reaction using an ab initio multistructure valence-bond approach. The orthogonalized Moffit (OM) method is employed to apply a correction for the large errors made by the ab initio calculation in representing the F⁻ ion relative to the F atom. The OM method predicts the potential surface to be of the highly “attractive” or “early downhill” type and to possess a potential energy well with respect to dissociation to the products LiF + F. The attributes of the surface predicted by the OM method are compared with those suggested by experiment and used in trajectory calculations for analogous systems.     

The equations-of-motion method for F2: Transition energies,oscillator strengths and born cross sections

The equations-of-motion method has been used to study various electronic states of F₂. The transition energies have been found in both the random phase approximation (RPA) and higher random approximation (HRPA) using single particle—hole components in the excitation operators. We have also computed generalized oscillator strengths (Born cross sections) for the scattering of high energy electrons by F₂.     

Comparison of close-coupling and approximate methods for F(2P12) + H2 non-reactive collisions: Translational wavefunction analysis

Electronic-rotational energy transfer in F(²P_{$\text{1}\text{2}$}) + H₂ (j = 0) non-reactive collisions is studied by analyzing the translational wavefunctions (TW) and transition probabilities of four model problems: full close-coupling (CC), diabatic (DDW) and adiabatic (ADW) distorted-wave Born theories, and an asymptotic sine-wave model. Comparisons among the approximate models are discussed and their accuracy is examined. DIM theory provides the diabatic electronic matrix elements, and the close-coupled equations are solved by the R-matrix method. The resulting S-matrix elements times their appropriate asymptotic wavefunctions when propagated in along the reaction coordinate generate the TW. For the CC results, relations between the TW and the adiabatic electrotational energy correlation diagrams are emphasized, while for the other models the effects of classical turning points, diabatic energy level structure, unitarization techniques, and other dynamical factors on the state-to-state transition probabilities are examined.     

FN+Cl Ions from Ionized F2NCl: a Computational Investigation on the Structure and Reactivity toward H2O

We have used various ab initio methods and basis sets to ascertain that the FN⁺Cl cation has a singlet ground state, ¹A′, which is more stable than the triplet state ³A″ by ca. 30 kcal mol^?1. We have subsequently used the Gaussian‐3 (G3) theory to explore the potential‐energy profile for the reaction between singlet FN⁺Cl and H₂O. The process commences by the effortless formation of a FN⁺Cl/H₂O complex, which, in principle, can undergo several alternative processes, including isomerization to N‐protonated FN(Cl)OH, 1,2‐elimination of HX (X=F or Cl), and 1,1‐loss of H₂. However, the energy barriers of all these processes are invariably larger than the energy (+18.1 kcal mol^?1) required for the formation of FN⁺Cl/H₂O from FN⁺Cl and H₂O, thus suggesting that, under gas‐phase thermal conditions, FN⁺Cl should be essentially unreactive toward H₂O. Comparing these theoretical findings with those concerning the reaction between FN⁺H, ClN⁺H, F₂N⁺, and H₂O, the reactivity order FN⁺H>F₂N⁺>ClN⁺H>FN⁺Cl, was derived, which parallels the trend we recently found by G2MS calculations concerning the Lewis acidity of these ions. This suggests the conceivable occurrence of correlations between the reactivity and thermochemical properties of these simple halonitrenium ions.     

用分子束研究.F(^2P)与CH3F和CH3Cl的化学反应

近年来, 我们在研究含氟烯烃和烷烃的红外激光诱导氧化和氯化反应的基础上, 深入研究了红外激光诱导卤代烷烃的脱卤化氢并生成: CF2卡宾和:CFCF3卡宾的反应[1-4]以往的研究往往是根据反应产物推论反应机理, 认为在反应过程中存在着卡宾中间体,但在实验中未能直接检测到. Kakimoto[5,6]曾报道过在流动体系中测到了.F+CH3F和.F+CH3Cl反应中:CHF和:CHCl的激光荧光激发谱, 但没有讨论卡宾形成的机理.Hirota[7]在讨论.F+CH3F反应时, 认为:CHF可能由攫氢过程产生而对于.F+CH3Cl反应同时生成:CHF和:CHCl未做说明. 本实验中用扩散分子束代替了流动反应体系, 从而大大减少了产物和反应物气体分子间的猝灭过程, 获得了信噪比大而清晰的图谱, 由此确证了:CHF和:CHCl的存在, 说明了.F+CH3Cl反应中自由基攫氢过程和偶合反应过程共存的反应历程. 这一结论对红外激光诱导一碳卤代宾化学反应机理研究有重要参考意义.     

Rates of reaction of atomic oxygen with C2H3F,C2H3Cl,C2H3Br, 1,1-C2H2F2, and 1,2-C2H2F2

Rate constants for the reactions of atomic oxygen (O³P) with C₂H₃F, C₂H₃Cl, C₂H₃Br, 1,1-C₂H₂F₂, and 1,2-C₂H₂F₂ have been measured at 307°K using a discharge-flow system coupled to a mass spectrometer. The rate constants for these reactions are (in units of 10¹¹ cm³ mole^?1 s^?1) 2.63 ± 0.38, 5.22 ± 0.24, 4.90 ± 0.34, 2.19 ± 0.18, and 2.70 ± 0.34, respectively. For some of these reactions, the product carbonyl halides were identified.     

Angular distributions for the F+H(2)-->HF+H reaction: the role of the F spin-orbit excited state and comparison with molecular beam experiments

We report quantum mechanical calculations of center-of-mass differential cross sections (DCS) for the F+H(2)-->HF+H reaction performed on the multistate [Alexander-Stark-Werner (ASW)] potential energy surfaces (PES) that describe the open-shell character of this reaction. For comparison, we repeat single-state calculations with the Stark-Werner (SW) and Hartke-Stark-Werner (HSW) PESs. The ASW DCSs differ from those predicted for the SW and HSW PES in the backward direction. These differences arise from nonadiabatic coupling between several electronic states. The DCSs are then used in forward simulations of the laboratory-frame angular distributions (ADs) measured by Lee, Neumark, and co-workers [J. Chem. Phys. 82, 3045 (1985)]. The simulations are scaled to match experiment over the range 12 degrees 相似文献   

Kinetics and mechanism of the addition of trichloromethyl radicals to chloroethylenes. The addition to CIS-C2Cl2H2, trans-C2Cl2H2, and C2Cl3H

The addition reactions of CCl₃ radicals with cis-C₂Cl₂H₂, trans-C₂Cl₂H₂, and C₂Cl₃H in liquid cyclohexane–CCl₄ mixtures were studied between 323 and 448 K. The Arrhenius parameters of these reactions were competitively determined versus H-atom transfer from cyclohexane and addition to C₂Cl₄. The present data and the data obtained in previous liquid and gas phase studies show that the reactivities displayed in addition reactions of different radicals with chloroethylenes reflect primarily variations in activation energies rather than in A factors. The activation energies for the addition of CCl₃, CF₃, and CH₃ radicals to chloroethylenes appear, to a large extent, to be determinedby the stability of the adduct radicals. Comparison of the reactivity trends in the addition reactions of chloro- and fluoro-substitutedethylenes indicates that these two electron-withdrawing substituentshave a converse effect on the reactivity of electrophilic radicals. This behavior is ascribed to the strong mesomeric effect of vinylic chlorosubstituents.