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1.
A new quantum scattering approach (linear combination of arrangement channels-scattering wavefunction,LCAC-SW) proposed by Deng and his co-workers is used to calculate collinear state-to-state reaction probabilities for the F + H-2(v)→HF(v')+H system.Several interesting problems such as threshold energy,compound states and enhance by translational energy of the reactants and the vibration excitation of products are discussed and they are compared with other theoretical investigations reported in the literature.It is shown that the LCAC-SW approach is the successful one of quantum scattering methods. 相似文献
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《Tetrahedron》1969,25(22):5509-5516
The thermal reaction of several types of Mannich bases with a variety of ketones, has been studied to establish the yield and structure of the product in each case. An attempt has been made to define the optimum reaction conditions. 相似文献
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Eyles CJ Brouard M Chadwick H Hornung B Nichols B Yang CH Kłos J Aoiz FJ Gijsbertsen A Wiskerke AE Stolte S 《Physical chemistry chemical physics : PCCP》2012,14(16):5403-5419
Fully Λ-doublet resolved state-to-state differential cross-sections (DCSs) for the collisions of the open-shell NO(X, (2)Π(1/2), ν = 0, j = 0.5) molecule with Ar at a collision energy of 530 cm(-1) are presented. Initial state selection of NO(X, (2)Π(1/2), j = 0.5, f) was performed using a hexapole so that the (low field seeking) parity of ε = -1, corresponding to the f component of the Λ-doublet, could be selected uniquely. Although the Λ-doublet levels lie very close in energy to one another and differ only in their relative parities, they exhibit strikingly different DCSs. Both spin-orbit conserving and spin-orbit changing collisions have been studied, and the previously unobserved structures in the fully quantum state-to-state resolved DCSs are shown to depend sensitively on the change in parity of the wavefunction of the NO molecule on collision. In all cases, the experimental data are shown to be in excellent agreement with rigorous quantum mechanical scattering calculations. 相似文献
5.
A full dimensional state-to-state quantum dynamics study is carried out for the prototypical complex-formation OH + CO → H + CO(2) reaction in the ground rovibrational initial state on the Lakin-Troya-Schatz-Harding potential energy surface by using the reactant-product decoupling method. With three heavy atoms and deep wells on the reaction path, the reaction represents a huge challenge for accurate quantum dynamics study. This state-to-state calculation is the first such a study on a four-atom reaction other than the H(2) + OH ? H(2)O + H and its isotope analogies. The product CO(2) vibrational and rotational state distributions, and product energy partitioning information are presented for ground initial rovibrational state with the total angular momentum J = 0. 相似文献
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Initial state-selected reaction probabilities for the H+CH(4)→H(2)+CH(3) reaction are computed for vanishing total angular momentum by full-dimensional calculations employing the multiconfigurational time-dependent Hartree approach. An ensemble of wave packets completely describing reactivity for total energies up to 0.58 eV is constructed in the transition state region by diagonalization of the thermal flux operator. These wave packets are then propagated into the reactant asymptotic region to obtain the initial state-selected reaction probabilities. Reaction probabilities for reactants in all rotational states of the vibrational 1A(1), 1F(2), and 1E levels of methane are presented. Vibrational excitation is found to decrease reactivity when reaction probabilities at equivalent total energies are compared but to increase reaction probabilities when the comparison is done at the basis of equivalent collision energies. Only a fraction of the initial vibrational energy can be utilized to promote the reaction. The effect of rotational excitation on the reactivity differs depending on the initial vibrational state of methane. For the 1A(1) and 1F(2) vibrational states of methane, rotational excitation decreases the reaction probability even when comparing reaction probabilities at equivalent collision energies. In contrast, rotational energy is even more efficient than translational energy in increasing the reaction probability when the reaction starts from the 1E vibrational state of methane. All findings can be explained employing a transition state based interpretation of the reaction process. 相似文献
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Quantum Monte Carlo (QMC) calculations on the stacked (st) and Watson/Crick (wc) bound adenine/thymine (A/T) and cytosine/guanine (C/G) DNA base pair complexes were made possible with the first large scale distributed computing project in ab initio quantum chemistry, Quantum Monte Carlo at Home (QMC@HOME). The results for the interaction energies (wc-A/T = 15.7 kcal/mol, wc-C/G = 30.2 kcal/mol, st-A/T = 13.1 kcal/mol, st-C/G = 19.6 kcal/mol) are in very good agreement with the best known coupled-cluster based estimates. The accuracy of these values is further supported by calculations on the S22 benchmark set of noncovalently bound systems, for which we obtain a small mean absolute deviation of 0.68 kcal/mol. Our results support previous claims that the stacking energies are of comparable magnitude to the interactions of the commonly discussed hydrogen-bonded motif. Furthermore, we show that QMC can serve as an advantageous alternative to conventional wave function methods for large noncovalently bound systems. We also investigated in detail all technical parameters of the QMC simulations and recommend a careful optimization procedure of the Jastrow correlation factors in order to obtain numerically stable and reliable results. 相似文献
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《Tetrahedron》1965,21(5):1049-1053
The reaction of benzoyl peroxide with various alkali and onium iodides were studied in both 95.1% and absolute ethanol. The nature of the cation exerts a remarkable effect on the rate, and, in a series of alkalide iodides, the rate constant increases in the order: Li+ < Na+ < K+ < Cs+ < Rb+. This order coincides with the order of their limiting conductance values, which reflect the size of solvated ions. It is concluded that the cation participates in the rate determining step of the reaction and stabilizes the negative charge which is developing on the oxygen atom of benzoyl peroxide in consequence of the electron-transfer from an iodide ion; with the cation of smaller size, this stabilization will be stronger, resulting in enhanced rate. The reaction with triethylsulphonium iodide is faster than with tetraethylammonium iodide; this fact is explained in terms of the structue of the sulphonium cation. 相似文献
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Jerzy Stanek 《Central European Journal of Chemistry》2011,9(4):737-742
An approximate analytical solution of the radial Schr?dinger equation for the generalized Hulthén potential is obtained by
applying an improved approximation of the centrifugal term. The bound state energy eigenvalues and the normalized eigenfunctions
are given in terms of hypergeometric polynomials. The results for arbitrary quantum numbers n
r
and l with different values of the screening parameter δ are compared with those obtained by the numerical method, asymptotic iteration,
the Nikiforov-Uvarov method, the exact quantization rule, and variational methods. The results obtained by the method proposed
in this work are in a good agreement with those obtained by other approximate methods.
相似文献
11.
N. P. Gnusin N. P. Berezina N. A. Kononenko O. A. Demina L. A. Annikova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(1):107-110
The approaches to the evaluation of the conductivity of ion-exchange columns are analyzed. Specifically, the three-wire model and Lichtenecker’s power equation are examined. The problem of how the coefficient of ion-exchange column filling and the parameter characterizing the state of conducting phases with respect to the current flow are related to the parameters involved in the equations of the three-wire model is treated theoretically. The common points and the coincident portions of the functions obtained in each of the approaches and some discrepancies between the functions are found. The discrepancies are determined by the special features of the models under consideration. Original Russian Text ? N.P. Gnusin, N.P. Berezina, N.A. Kononenko, O.A. Demina, L.A. Annikova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 1, pp. 122–126. 相似文献
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An accurate potential energy surface for the ground electronic state of SH3 system has been constructed with 41,882 high level ab initio energy points and the neural network fitting method. The time-dependent wave packet method has been used to calculate the first state-to-state differential cross sections for the title reaction up to 1.2 eV in full dimensions, based on the reactant–product decoupling scheme. It is found that the majority of H2S are produced in the ground vibrational state, with a large fraction of available energy for the reaction ending up as product translational motion. The differential cross sections at the threshold energy are dominated by a very narrow peak in the backward direction. With the increase of collision energy, the width of the angular distribution increases considerably, which is a typical feature of a direct reaction via abstract mechanism, similar to the H2 + OH → H2O + H reaction. © 2018 Wiley Periodicals, Inc. 相似文献
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Abdul-Majid Wazwaz 《Journal of mathematical chemistry》2014,52(2):613-626
In this paper, we establish the Volterra integro-differential forms of the Lane–Emden equations. We use the variational iteration method (VIM) to effectively treat these forms. The Volterra integro-differential forms of the Lane–Emden equations overcome the singular behavior at the origin $x=0$ and do not use a variety of Lagrange multipliers. Several numerical examples are examined to show the validity of the integro-differential forms. 相似文献
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The detailed reaction pathways for the ammonium cyanate transformation into urea (W?hler's reaction) in the gas phase, in solution, and in the solid state have exhaustively been explored by means of first-principles quantum chemical calculations at the B3LYP level of theory using the 6-31G(d,p) basis set. This serendipitous synthesis of urea is predicted to proceed in two steps; the first step involves the decomposition of the ammonium cyanate to ammonia and isocyanic or cyanic acid, and the second one, which is the main reaction step (and probably the rate-determining step), involves the interaction of NH(3) with either isocyanic or cyanic acid. Several alternative pathways were envisaged for the main reaction step of W?hler's reaction in a vacuum involving the formation of "four-center" transition states. Modeling W?hler's reaction in aqueous solution and in the solid state, it was found that the addition of NH(3) to both acids is assisted (autocatalyzed) by the active participation of extra H(2)O and/or NH(3) molecules, through a preassociative, cooperative, and hydrogen-transfer relay mechanism involving the formation of "six-center" or even "eight-center" transition states. The most energetically economic path of the rate-determining step of W?hler's reaction is that of the addition of NH(3) to the C=N double bond of isocyanic acid, directly affording urea. An alternative pathway corresponding to the anti-addition of ammonia to the Ctbd1;N triple bond of cyanic acid, yielding urea's tautomer HN=C(OH)NH(2), seems to be another possibility. In the last case, urea is formed through a prototropic tautomerization of its enolic form. The energies of the reactants, products, and all intermediates along with the barrier heights for each reaction path have been calculated at the B3LYP/6-31G(d,p) level of theory. The geometry optimization and characterization of all of the stationary points found on the potential energy hypersurfaces was performed at the same level of theory. 相似文献
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We present converged exact quantum wave packet calculations of reaction probabilities, integral cross sections, and thermal rate coefficients for the title reaction. Calculations have been carried out on the ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged wave packet reaction probabilities at selected values of the total angular momentum up to a partial wave of J = 140 with the HCl reagent initially selected in the v = 0, j = 0-16 rovibrational states have been obtained for the collision energy range from threshold up to 0.8 eV. The present calculations confirm an important enhancement of reactivity with rotational excitation of the HCl molecule. First, accurate integral cross sections and rate constants have been calculated and compared with the available experimental data. 相似文献
16.
《Tetrahedron》1968,24(15):5311-5321
In a spectrophotometric investigation of the base-catalysed isomerization of anthrone to anthranol, reaction rates were measured in the presence of varying concentrations of the base and in various solvents, including inert hydrocarbons. The enolization reaction was found to be of the first order both for anthrone and the base. The mechanism involves reaction of the ketone with the base to give a hydrogen-bonded complex between the enol and base, which is in equilibrium at any one instant with the free enol and base. As the rate constant depends on the polarity of the solvent as well as on the strength of the base, the rate-determining step involves a highly polar transition state. It is concluded that the base-catalysed isomerization takes place through an intramolecular proton transfer where the base acts as a proton carrier. 相似文献
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《Tetrahedron》1963,19(6):817-820
The reaction of sulphoxides with at least one methyl or methylene group with carboxylic acid anhydride, called the Pummerer reaction, gives α-acyloxy derivatives of the corresponding sulphide. The mechanism of this reaction was studied by oxygen-18 tracer technique. The reaction between dimethyl sulphoxide and acetic anhydride appears to proceed through an intermolecular rearrangement by nucleophilic attack of acetate anion on methylene carbon atom of the intermediate II. The implications of this reaction and the enzymatic oxidative demethylation are considered in connection with a previous investigation with t-amine N-oxides. 相似文献
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The title reaction is thought to be responsible for the production of molecular nitrogen in interstellar clouds. In this work, we report quantum capture calculations on a new two-dimensional potential energy surface determined by interpolating high-level ab initio data. The low-temperature rate constant calculated using a capture model is quite large and has a positive temperature dependence, in agreement with a recent experiment. The origin of the aforementioned behaviors of the rate constant is analyzed. 相似文献
19.
Fleming DG Arseneau DJ Sukhorukov O Brewer JH Mielke SL Truhlar DG Schatz GC Garrett BC Peterson KA 《The Journal of chemical physics》2011,135(18):184310
The neutral muonic helium atom (4)Heμ, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation (μSR) measurements of the chemical reaction rate constant of (4)Heμ with molecular hydrogen, (4)Heμ + H(2) → (4)HeμH + H, at temperatures of 295.5, 405, and 500 K, as well as a μSR measurement of the hyperfine coupling constant of muonic He at high pressures. The experimental rate constants, k(Heμ), are compared with the predictions of accurate quantum mechanical (QM) dynamics calculations carried out on a well converged Born-Huang (BH) potential energy surface, based on complete configuration interaction calculations and including a Born-Oppenheimer diagonal correction. At the two highest measured temperatures the agreement between the quantum theory and experiment is good to excellent, well within experimental uncertainties that include an estimate of possible systematic error, but at 295.5 K the quantum calculations for k(Heμ) are below the experimental value by 2.1 times the experimental uncertainty estimates. Possible reasons for this discrepancy are discussed. Variational transition state theory calculations with multidimensional tunneling have also been carried out for k(Heμ) on the BH surface, and they agree with the accurate QM rate constants to within 30% over a wider temperature range of 200-1000 K. Comparisons between theory and experiment are also presented for the rate constants for both the D + H(2) and Mu + H(2) reactions in a novel study of kinetic isotope effects for the H + H(2) reactions over a factor of 36.1 in isotopic mass of the atomic reactant. 相似文献
20.
Glass-Maujean M Jungen Ch Schmoranzer H Haar I Knie A Reiss P Ehresmann A 《The Journal of chemical physics》2011,135(14):144302
The energies, widths and absolute intensities of the P(1) v' = 0, J' = 1 absorption transitions of H(2) have been measured in the spectral range of 81-75 nm using monochromatized synchrotron radiation. This work completes and extends previous observations, in particular those of Herzberg and Jungen [J. Mol. Spectrosc. 41, 425 (1972)]. Ab initio multichannel quantum defect theory (MQDT) is used to corroborate the spectral analysis of the experimental data. Line intensities and decay widths are also calculated using MQDT. 相似文献