Stereo-dynamics of the exchange reaction HaWLiHb → LiHa＋Hb and its isotopic variants

<正>The quasi-classical trajectory(QCT) method is used to calculate the stereo-dynamics of the exchange reaction H_a+LiH_b→LiH_a+H_b and its isotopic variants based on an accurate potential energy surface reported by Prudente et al.[Prudente F V,Marques J M C and Maniero A M 2009 Chem.Phys.Lett.474 18].The reactive probability of the title reaction is computed.The vector correlations and four polarization-dependent generalized differential cross sections(PDDCSs) at different collision energies are presented.The influences of the collision energy and the reagent rotation on the product polarization are studied in the present work.The results indicate that the product rotational angular momentum j’ is not only aligned,but also oriented along the direction perpendicular to the scattering plane. The product polarization distributions of the title reaction and its isotopic variants exhibit distinct differences which may arise from different mass combinations.     

Effects of a reagent＇s rotational and vibrational excitations on reactionO（3p）＋ H2（v=0, 3, j = 0, 3, 5, 7, 9, 12, 15） → OH ＋ H

To investigate the effect of a reagent’s rotational and vibrational excitations on the stereo-dynamics of the reaction product, the title reaction is theoretically simulated using the quasi-classical trajectory (QCT) method on the 3 A and 3 A potential energy surfaces (PESs). The reaction cross section is considered as the only scalar property in this work at four different collision energies. Furthermore the vector properties including two polarization-dependent differential cross sections (PDDCSs), the angular distributions of product’ rotational momentum are discussed at one fixed collision energy. Effects of reagents’ rotational excitation on the reaction do exist regularly.     

Vector correlations study of the reaction N(~2D) + H_2(X~1Σ_g~+) →NH(a~1?) + H(~2S) with different collision energies and reagent vibration excitations

Vector correlations of the reaction N(2D)+ H2(X1Σ+g) → NH(a1?)+ H(2S) are studied based on a recent DMBESEC PES for the first excited state of NH2[J. Phys. Chem. A 114 9644(2010)] by using a quasi-classical trajectory method.The effects of collision energy and the reagent initial vibrational excitation on cross section and product polarization are investigated for v = 0–5 and j = 0 states in a wide collision energy range(10–50 kcal/mol). The integral cross section could be increased by H2 vibration excitation remarkably based on the DMBE-SEC PES. The different phenomena of differential cross sections with different collision energies and reagent vibration excitations are explained. Particularly,the NH molecules are scattered mainly in the backward hemisphere at low vibration quantum number and evolve from backward to forward direction with increasing vibration quantum number, which could be explained by the fact that the vibrational excitation enlarges the H–H distance in the entrance channel, thus enhancing the probability of collision between N atom and H atom. A further study on product polarization demonstrates that the collision energy and vibrational excitation of the reagent remarkably influence the distributions of P(θr), P(φr), and P(θr, φr).     

Effects of the vibrational and rotational excitation of reagent on the stereodynamics of the reaction S（3P） + H2→ SH + H

Quasiclassical trajectory （QCT） calculations are first carried out to study the stereodynamics of the S （3p） ＋ H2 → SH ＋ H reaction based on the ab initio 13Atr potential energy surface （PES） （Lii etal. 2012 J. Chem. Phys. 136 094308）. The QCT-calculated reaction probabilities and cross sections for the S ＋ H2 （v = 0, j = 0） reaction are in good agreement with the previous quantum mechanics （QM） results. The vector properties including the alignment, orientation, and polarization- dependent differential cross sections （PDDCSs） of the product SH are presented at a collision energy of 1.8 eV. The effects of the vibrational and rotational excitations of reagent on the stereodynamics are also investigated and discussed in the present work. The calculated QCT results indicate that the vibrational and rotational excitations of reagent play an important role in determining the stereodynamic properties of the title reaction.     

Effect of Reagent Vibrational and Rotational Excitation on the F＋H2 Reaction： Theoretical Study of the Stereodynamics Using Quasi-Classical Trajectory Method

The vector correlations in the reaction F＋H2 （v =0-3, j =0-3）→ HF（v＇, j＇）＋H are investigated using the quasi- classical trajectory method on the Stark-Werner potential energy surface at a collision energy of 1.0eV. The potential distribution P（θr） to angles between k and j＇, the distribution P（Фr） to dihedral angles, denoting k - k＇ - j＇ correlation and the polarization-dependent generalized differential cross sections, are calculated. The effect of reagent vibrational and rotational excitation on the F＋H2 reaction is discussed in detail The results suggest that the different vibrational and rotational quantum states of H2 have different influences on the product polarization.     

Effect of ro-vibrational excitation of NeH~+ on the stereodynamics for the reactions H+NeH~+(v=1-3,j=1,3,5) →H_2~++Ne

The stereodynamics of the abstraction reaction H + NeH+(v = 1-3,j = 1,3,5) → H2+ + Ne is studied theoretically with a quasi-classical trajectory method on a new ab initio potential energy surface [ S J,Zhang P Y,Han K L and He G Z 2012 J.Chem.Phys.132 014303].The effects of vibrational and rotational excitation of reagent molecules on the polarization of the product are investigated.The reaction cross sections,the distributions of P(θr),P(φr),and polarizationdependent differential cross sections(PDDCSs) are calculated.The obtained cross sections indicate that the title reaction is a typical barrierless atom(ion)-ion(molecule) reaction.The initial vibrational excitation and rotational excitation of reagent molecules have distinctly different influences on stereodynamics of the title reaction,and the possible reasons for the differences are presented.     

Effects of collision energy and rotational quantum number on stereodynamics of the reactions:H(~2S)+NH(v=0,j=0,2,5,10)→N(~4S)+H_2

The stereodynamical properties of H(~2S) + NH(v = 0,j = 0,2,5,10)→N(~4S) + H_2 reactions are studied in this paper by using the quasi-classical trajectory(QCT) method with different collision energies on the double many-body expansion(DMBE) potential energy surface(PES)(Poveda L A and Varandas A J C 2005 Phys.Chem.Chem.Phys.7 2867).In a range of collision energy from 2 to 20 kcal/mol,the vibrational rotational quantum numbers of the NH molecules are specifically investigated on v = 0 and j = 0,2,5,10 respectively.The distributions of P(θ_r),P(φ_r),P(θ_r,φ_r),(2π/σ)(dσ_(00)/dω_t)differential cross-section(DCSs) and integral cross-sections(ICSs) are calculated.The ICSs,computed for collision energies from 2 kcal/mol to 20 kcal/mol,for the ground state are in good agreement with the cited data.The results show that the reagent rotational quantum number and initial collision energy both have a significant effect on the distributions of the k-j',the k-k'-j',and the k-k' correlations.In addition,the DCS is found to be susceptible to collision energy,but it is not significantly affected by the rotational excitation of reagent.     

Theoretical prediction of the optimal conditions for observing the stereodynamical vector properties of the C（3P）＋OH （X2∏）→CO（X1S＋）＋H（2S） reaction

The best optimal initial reactant state and collision energy for observing the stereodynamical vector properties of the title reaction in the ground electronic state X2A’ potential energy surface （PES）[Zanchet et al. 2006 J. Phys. Chem. A 110 12017] are theoretically predicted using the quasi-classical trajectory （QCT） method for the first time. The calculated results reveal that the smallest value of the rotational quantum number j, larger vibrational quantum number v, and the lower strength of collision energy should be selected for offering the most obvious picture about the stereodynamical vector properties. Polarization-dependent differential cross sections and the angular momentum alignment distribution, P（θr） and P（Φr） in the center-of-mass frame, are obtained to gain an insight into the alignment and orientation of the product molecules. The rotational angular momentum vector j’ of CO is aligned to be perpendicular to reagent relative velocity k. The product polarizations align along the y axis, pointing to the positive direction of the y axis. A new method is developed to investigate massive reactions with various initial states and to further study the vector properties of the fundamental reactions in detail.     

Theoretical prediction of the optimal conditions for observing the stereodynamical vector properties of the C(~3P) + OH(X~2Π) → CO(X~1 Σ~+) + H(~2S) reaction

The best optimal initial reactant state and collision energy for observing the stereodynamical vector properties of the title reaction in the ground electronic state X2A potential energy surface(PES) [Zanchet et al. 2006 J. Phys. Chem. A 110 12017] are theoretically predicted using the quasi-classical trajectory(QCT) method for the first time. The calculated results reveal that the smallest value of the rotational quantum number j, larger vibrational quantum number v, and the lower strength of collision energy should be selected for offering the most obvious picture about the stereodynamical vector properties. Polarization-dependent differential cross sections and the angular momentum alignment distribution, P(θr) and P(Φr) in the center-of-mass frame, are obtained to gain an insight into the alignment and orientation of the product molecules. The rotational angular momentum vector j of CO is aligned to be perpendicular to reagent relative velocity k. The product polarizations align along the y axis, pointing to the positive direction of the y axis. A new method is developed to investigate massive reactions with various initial states and to further study the vector properties of the fundamental reactions in detail.     

Influence of reagent vibration on the stereodynamics of the Li ＋ HF → LiF ＋ H reaction

We investigate the influence of reagent vibration on the stereodynamics of the title reaction by the quasi-classical trajectory on the Aguado-Paniagua2-potential energy surface developed by Aguado et al.(J.Chem.Phys.1997 106 1013).The cross sections and reaction probability as functions of the reagent vibration are calculated in the centre-ofmass frame.The product angular distributions of p(θr),p(φr),and p(θr,φr),which reflect the vector correlation,are also presented and discussed.The results indicate that the vector properties are sensitively affected by the vibrational excitation.     

Stereodynamics study of the H′（^2S） ＋ NH（X^3∑-） 〉 N（4S） ＋ H2 reaction

The stereodynamics and reaction mechanism of the H′（^2S） ＋ NH （X^3∑^-） → N（^4S） ＋ H2 reaction are thoroughly studied at collision energies in the 0.1 eV-1.0 eV range using the quasiclassical trajectory （QCT） on the ground 4A″ potential energy surface （PES）. The distributions of vector correlations between products and reagents P（φr）, P（φr） and P（φr,φr） are presented and discussed. The results indicate that product rotational angular momentum j′ is not only aligned, but also oriented along the direction perpendicular to the scattering plane; further, the product H2 presents different rotational polarization behaviors for different collision energies. Furthermore, four polarization-dependent differential cross sections （PDDCSs） of the product He are also calculated at different collision energies. The reaction mechanism is analyzed based on the stereodynamics properties. It is found that the abstraction mechanism is appropriate for the title reaction.     

Translational,vibrational,rotational enhancements and alignments of reactions H + ClF(v = 0-5,j= 0,3,6,9) →HCl + F and HF + Cl,at E_(rel)= 0.5-20 kcal/mol

Quasi-classical trajectory calculations of the title reactions H + ClF(v = 0 5,j= 0,3,6,9) →HCl + F and HF + Cl,at E_(rel)= 0.5 20 kcal/mol–20 kcal/mol on ground potential energy surface DHTSN of 12A[M.P.Deskevich,M.Y.Hayes,K.Takahashi,R.T.Skodje and D.J.Nesbitt,J.Chem.Phys.124,224303(2006)] are performed.Potential energy surfaces derived from DHTSN for the title reactions are obtained,and compared with that of DHTSN for the reaction F + HCl → HF + Cl.Both potential energy surfaces have an early barrier pattern.Integral cross sections and alignments of product molecules HCl and HF dependent on the internal energy states v and j of reactant molecule ClF are obtained and compared.Translational,vibrational,and rotational energy specific translational enhancements of the reactant molecule ClF of the title reactions are found.Reaction mechanisms of the title reactions according to the respective potential energy contours are further found and explained.Reasons of simultaneous translational and vibrational enhancements are clarified.     

The effect of collision energy on the stereodynamics of the reaction H(~2S)+NH(X~3∑~-,v = 0,j = 0)→ N(~4S)+H_2

The quasi-classical trajectory(QCT) is calculated to study the stereodynamics properties of the title reaction H(2S)+NH(X3∑-) →N(4S)+H2 on the ground state 4A' potential energy surface(PES) constructed by Zhai and Han [2011 J.Chem.Phys.135 104314].The calculated QCT reaction probabilities and cross sections are in good agreement with the previous theoretical results.The effects of the collision energy on the k-k' distribution and the product polarization of H2 are studied in detail.It is found that the scattering direction of the product is strongly dependent on the collision energy.With the increase in the collision energy,the scattering directions of the products change from backward scattering to forward scattering.The distribution of P(θr) is strongly dependent on the collision energy below the lower collision energy(about 11.53 kcal/mol).In addition,the P(φr) distribution dramatically changes as the collision energy increases.The calculated QCT results indicate that the collision energy plays an important role in determining the stereodynamics of the title reaction.     

Energy and rotation-dependent stereodynamics of H(~2S) + NH(a~1?) → H_2(X~1Σ_g~+) + N(~2D) reaction

Quasi-classical trajectory calculations are performed to study the stereodynamics of the H(~2S) + NH(a~1?) →H_2(X~1Σ_g~+) + N(~2D) reaction based on the first excited state NH_2(1~2A') potential energy surface reported by Li et al.[Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644] for the first time. We observe the changes of differential cross-sections at different collision energies and different initial reagent rotational excitations. The influence of collision energy on the k–k' distribution can be attributed to a purely impulsive effect. Initial reagent rotational excitation transforms the reaction mechanism from insertion to abstraction. The effect of initial reagent rotational excitations on k–k' distribution can be explained by the rotational excitation enlarging the rotational rate of reagent NH in the entrance channel to reduce the probability of collision between incidence H atom and H atom of target molecular. We also investigate the changes of vector correlations and find that the rotational angular momentum vector j' of the product H_2 is not only aligned, but also oriented along the y axis. The alignment parameter, the disposal of total angular momentum and the reaction mechanism are all analyzed carefully to explain the polarization behavior of the product rotational angular moment.     

Stereodynamics of the He ＋ D2^＋ → HeD^＋ ＋ D Reaction on the PALMIERI Surface

Using the quasi-classical trajectory method, the product rotational polarization of the ion-molecule reaction He^＋D2^＋ has been calculated at different collision energies on the PALMIERI potential energy surface [Palmieri et al. Mol. Phys. 98 （2000） 1835]. The distribution angle between k and j′, P（Or）, the distribution of the dihedral angle P（Фr）, and the angular distribution of product rotational vectors in the form of polar plots in θr and Фr are calculated. In addition, four polarization-dependent differential cross sections are also presented in the center-of-mass frame, respectively. The results indicate that the rotational polarization of the product HeD^＋ presents different characters for different collision energies. These discrepancies may be ascribed to the different collision energies and constructions of the potential energy surface.     

Mechanism analysis of reaction S~+(~2D)+H_2(X~1Σ_g~+) → SH~+(X~3Σ~-) + H(~2S) based on the quantum state-to-state dynamics

We present a state-to-state dynamical calculation on the reaction S~++ H_2→ SH~+ +H based on an accurate ~X2 A~″ potential surface. Some reaction properties, such as reaction probability, integral cross sections, product distribution, etc.,are found to be those with characteristics of an indirect reaction. The oscillating structures appearing in reaction probability versus collision energy are considered to be the consequence of the deep potential well in the reaction. The comparison of the present total integral cross sections with the previous quasi-classical trajectory results shows that the quantum effect is more important at low collision energies. In addition, the quantum number inversion in the rotational distribution of the product is regarded as the result of the heavy–light–light mass combination, which is not effective for the vibrational excitation. For the collision energies considered, the product differential cross sections of the title reaction are mainly concentrated in the forward and backward regions, which suggests that there is a long-life intermediate complex in the reaction process.     

Theoretical study of stereodynamics for the O（3P） ＋ H2 → OH ＋ H reaction

This paper employs the quasi-classical trajectory calculations to study the influence of collision energy on the title reaction on the potential energy surface of the ground ³A' triplet state developed by Rogers et al. (J. Phys. Chem. A 2000 104 2308). It calculates the product angular distribution of P(θ_r), P(φ_r) and P(θ_r, φ_r) which reflects vector correlation. The distribution P(θ_r) shows that product rotational angular momentum vectors j' of the products are strongly aligned along the relative velocity direction k. The distribution of P(φ_r) implies a preference for left-handed product rotation in planes parallel to the scattering plane. Four different polarisation-dependent cross-sections are also presented in the centre-of-mass frame. Results indicate that OH is sensitively affected by collision energies of H₂.     

The collision energy effect on the stereodynamics of the Ca + HCl→CaCl + H reaction

The stereodynamics of the reaction of Ca + HCl are calculated at three different collision energies based on the potential energy surface [Verbockhaven G et al. 2005 J. Chem. Phys. 122 204307] using quasi-classical trajectory theory. The polarization-dependent differential cross sections (PDDCSs) (2π/σ )(dσ 00 /dω t ), (2π/σ )(dσ 20 /dωt ), (2π/σ )(dσ 22+ /dωt ), (2π/σ )(dσ 21 /dω t ) and the distributions of P(θ r ), P(φr ), and P(θr ,φr ) are calculated. The results indicate that the rotational polarization of the CaCl product presents different characteristics for the different collision energies, and the effects of the collision energy on the vector potential, including the alignment, orientation, and PDDCSs, are not obvious.     

Translational,vibrational, rotational enhancements and alignments of reactions H＋CIF （v = 0-5, j ： 0,3,6,9） 〉HCI＋F and HF＋CI,at EreI ： 0.5-20 kcal/mol

Quasi-classical trajectory calculations of the title reactions H ＋ C1F （v = 0-5, j = 0, 3,6, 9） -＋ HCl ＋ F and H ＋ C1F （v = 0-5, j =0, 3, 6, 9） → HF ＋ C1 at Erel = 0.5 kcal/mol-20 kcal/mol on ground potential energy surface DHTSN of 1 2AI [M. E Deskevich, M. Y. Hayes, K. Takahashi, R. T. Skodje and D. J. Nesbitt, J. Chem. Phys. 124, 224303 （2006）] are performed. Potential energy surfaces derived from DHTSN for the title reactions are obtained, and compared with that of DHTSN for the reaction F ＋ HC1 -＋ HF ＋ C1. Both potential energy surfaces have an early barrier pattern. Integral cross sections and alignments of product molecules HC1 and HF dependent on the internal energy states v and j of reactant molecule C1F are obtained and compared. Translational, vibrational, and rotational energy specific translational enhancements of the reactant molecule CIF of the title reactions are found. Reaction mechanisms of the title reactions according to the respective potential energy contours are further found and explained. Reasons of simultaneous translational and vibrational enhancements are clarified.     

Investigation of isotope effects of dynamic properties for H(D) +OF reactions by the quasi-classical trajectory method

Quasi-classical trajectory (QCT) calculations are employed to study the dynamic properties for \mbox{H(D)} + \mbox{OF} reactions on the adiabatic potential energy surface (PES) of the \mbox{1}{ }^{3}\mbox{A}' triplet state. Obvious differences between the reaction probabilities for J = 0, integral cross sections for J \ne 0, branch ratios of the product and internuclear distances as well as product rotational alignments between the title reactions are found. These differences are attributed mainly to the different reduced masses of the reactants and the different zero-point energies (ZPEs) of the transition state.