Stereodynamics of the reactions: F+H_2/HD/HT→FH+H/D/T

Among many kinds of ways to study the properties of atom and molecule collision, the quasi-classical trajectory(QCT) method is an effective one to investigate the molecular reaction dynamics. QCT calculations have been carried out to investigate the stereodynamics of the reactions F + H2/HD/HT→FH + H/D/T, which proceed on the lowest-lying electronic states of the FH2 system based on the potential energy surface(PES) of the 12A' FH2 ground state. Although the QCT method cannot describe all quantum effects in the process of the reaction, it has unique advantages when facing a three-atoms system or complicated polyatomic systems. Differential cross sections(DCSs) and three angle distribution functions P(θr), P(φr), P(θr, φr) on the PES at the collision of 2.74 kcal/mol have been investigated. The isotope effect becomes more obvious with the reagent molecule H2 turning into HD and HT. P(θr, φr), as the joint probability density function of both polar angles θr and φr, can reflect the properties of three-dimensional dynamic more intuitively.     

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 study of stereodynamics for the reaction O（3P）+D2（v= 0,j=0） → OD+D and isotope effect

Quasi-classical trajectory (QCT) calculations have been performed to study the product polarization behaviours in the reaction O(3P) + D2 (v = 0, j = 0) → OD + D. By running trajectories on the 3A and 3A potential energy surfaces (PESs), vector correlations such as the distributions of the polarization-dependent differential cross sections (PDDCSs), the angular distributions of P (θr) and P (φr) are presented. Isotope effect is discussed in this work by a comprehensive comparison with the reaction O(3P) + H2 (v = 0, j = 0) → H + H. Common characteristics as well as differences are discussed in product alignment and orientation for the two reactions. The isotope mass effect differs on the two potential energy surfaces: the isotope mass effect has stronger influence on P (θr) and PDDCSs of the 3A PES while the opposite on P (φr) of the 3A potential energy surface.     

Effect of isotope on state-to-state dynamics for reactive collision reactions ■ and ■ in ground state 1~2 A’’ and first excited 1~2 A’ potential energy surfaces

We carry out quantum scattering dynamics and quasi-classical trajectory(QCT) calculations for the O+H_2~+ reactive collision in the ground(1~2 A").nd first excited(1~2 A') potential energy surface.We calculate the reaction probabilities of O+H_2~+(v=0,j=0)→OH~++H and O+H_2~+(v=0,j=0)→OH+H~+reaction for total angular momentum J=0.The results calculated by QCT are consistent with those from quantum mechanical wave packet.Using the QCT method,we generate in the center-of-mass frame the product state-resolved integral cross-sections(ICSs);two commonly used generalized polarization-dependent differential cross-sections(PDDCS s),(2π/σ)(dσ_(00)/dω_t),(2π/σ)(dσ_(20)/dω_t));and three angular distributions of the product rotational vectors,p(θ_r),P(φ_r),and p(θ_r,φ_r).We discuss the influence on the scalar and vector properties of the potential energy surface,the collision energy,and the isotope mass.Since there are deep potential wells in these two potential energy surfaces,their kinetic characteristics are similar to each other and the isotopic effect is not obvious.However,the well depths and configurations of the two potential energy surfaces are different,so the effects of isotopic substitution on the integral cross-section and the rotational polarization of product are different.     

Quasi-classical trajectory study of the isotope effect on the stereodynamics in the reaction H（2S） + CH（X2Π;u= 0,j= 1） → C（1D） + H2（X1Σg+）

The isotope effect on the stereodynamic properties in the title reaction is investigated by a quasi-classical trajectory(QCT) method on the 11A potential energy surface at a collision energy of 23.06 kcal/mol. The angular distributions P(θr),P(φr), P(θr, φr), and the polarization-dependent generalized differential cross sections are calculated, which demonstrate the observable influences on the rotational polarization of the product by the isotopic substitution of H with D.     

Quasi-Classical Trajectory Study on Ar＋H2＋/D2＋/T2＋ Reactions

In order to explore the isotope effect on stereo dynamics, we investigate the trajectory calculations of Ar＋H2＋/D2＋/T2＋ and Ar＋T2＋ reactions on the ab initio potential energy surface constructed by us and calculate the distributions of product polarization P（θr）, P（r） and four generalized polarization-dependent differential cross-sections. The product rotational alignment parameters （P2（j＇ · k）） for the title reactions are compared and discussed with mass factors. Furthermore, the angular distributions of the product rotational vectors in the form of polar plot in θr and r are presented. The results indicate that the stereo dynamics properties of the title reactions are sensitive to the mass factor.     

Intrinsic product polarization and branch ratio in the S(~1D,~3P)+HD reaction on three electronic states

The intrinsic product polarization and intramolecular isotope effect of the S(~1D,~3P) + HD reaction have been investigated on both the lowest singlet state(1A) and the triplet state(3A and 3A) potential energy surfaces by using quasi-classical trajectory and quantum mechanical methods.The calculations indicate that intramolecular isotope effects are different on the three electronic states.The stereodynamics study shows that the P(θr) distributions,P(φ r) distributions,and polarization-dependent differential cross sections(PDDCSs)(00) are sensitive to mass factor and the product angular momentum vectors are not only aligned but also oriented.     

Quasi-classical trajectory study of the isotope effect on the stereodynamics in the reaction H（2S） ＋ CH（X2∏; v=o,j= 1）→ C（1D）＋H2（X1∑g＋）

The isotope effect on the stereodynamic properties in the title reaction is investigated by a quasi-classical trajectory （QCT） method on the 11At potential energy surface at a collision energy of 23.06 kcal/mol. The angular distributions P（φr ）, P（θr）, P（θr, φr）, and the polarization-dependent generalized differential cross sections are calculated, which demonstrate the observable influences on the rotational polarization of the product by the isotopic substitution of H with D.     

Influence of the reagent vibration on the stereo-dynamics of the reactions D^- ＋ H2 and H^- ＋ D2

Employing the quasi-classical trajectory method and the potential energy surface of Panda and Sathyamurhy [Panda A N and Sathyamurthy N 2004 J.Chem.Phys.121 9343],the effect of the reagent vibration on vector correlation of the ion-molecule reactions D～-+H₂ and H～-+D₂ is studied at a collision energy of 35.7 kcal/mol.Four generalized polarization-dependent differential cross sections （2π/σ）（dσ 00 /dωt）,（2π/σ）（dσ 20 /dωt）,（2π/σ）（dσ 22+ /dωt）,and （2π/σ）（dσ 21 /dωt） are presented in the centre-of-mass reference frame,separately.At the same time,the effects on the product angular distributions P （θr）,P （φr） and P （θr,φr） of the title reactions are also analysed.The calculated results show that the scattering tendencies of the product HD,the alignment and the orientation of j sensitively depend on reagent molecule vibration.     

Effect of reagent vibrational excitation and isotope substitution on the stereo-dynamics of the Ba+HF→BaF+H reaction

Based on an extended London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES), the Ba + HF reaction has been studied by the quasi-classical trajectory (QCT) method. The reaction integral cross section as a function of collision energy for the Ba + HF → BaF + H reaction is presented and the influence of isotope substitution on the differential cross sections (DCSs) and alignments of the product's rotational angular momentum have also been studied. The results suggest that the integral cross sections increase with increasing collision energy, and the vibrational excitation of the reagent has great influence on the DCS. In addition, the product's rotational polarization is very strong as a result of heavy-heavy-light (HHL) mass combination, and the distinct effect of isotope substitution on the stereodynamics is also revealed.     

The characteristics of O＋HD （v = 0, j = 0） reaction dynamics

The analytical potential energy function of HDO is constructed at first using the many-body expansion method.The reaction dynamics of O+HD(v = 0,j = 0) in five product channels are all studied by quasi-classical trajectory(QCT) method.The results show that the long-lived complex compound HDO is the dominant product at low collision energy.With increasing collision energy,O+HD → OH+D and O+HD → OD+H exchange reactions will occur with remarkable characteristics,such as near threshold energies,different reaction probabilities,and different reaction cross sections,implying the isotopic effect between H and D.With further increasing collision energy(e.g.,up to 502.08 kJ/mol),O+HD → O+H+D will occur and induce the complete dissociation into single O,H,and D atoms.     

Isotope effect on the stereodynamics for the collision reaction H＋LiF（v = 0, j = 0） → HF＋Li

Stereodynamics for the reaction H+LiF(v=0, j=0) → HF+Li and its isotopic variants on the ground-state (1 2 A′) potential energy surface (PES) are studied by employing the quasi-classical trajectory (QCT) method. At a collision energy of 1.0 eV, product rotational angular momentum distributions P (θr), P (φr), and P (θr ,φr), are calculated in the center-of-mass (CM) frame. The results demonstrate that the product rotational angular momentum j′ is not only aligned along the direction perpendicular to the reagent relative velocity vector k, but also oriented along the negative y axis. The four generalized polarization-dependent differential cross sections (PDDCSs) are also computed. The PDDCS 00 distribution shows a preferential forward scattering for the product angular distribution in each of the three isotopic reactions, which indicates that the title collision reaction is a direct reaction mechanism. The isotope effect on the stereodynamics is revealed and discussed in detail.     

Theoretical Study of Isotopic Effect of Oxygen Atom on the Stereodynamics for the O（^3P） ＋ D2 → OD ＋ D Reaction

Quasi-classical trajectory theory is used to study the isotope effect of oxygen atoms on the vector correlations in the O（^3P） ＋ D reaction at a collision energy of 25kcal/mol using accurate potential energy surface of the 3A＇ triplet state. The distributions of p（θr） and the distribution of dihedral angel p（φr） as well as p（θr,φr） are calculated. Moreover, four polarization-dependent generalized differential cross sections （PDDCSs） of product are presented in the center-of-mass frame. The results indicate that the polarization of the product presents different characters for the isotope effect of oxygen atoms. Isotopic substitute can cause obviously different effects on the four PDDCSs.     

Theoretical prediction of energy dependence for D+BrO→DBr+O reaction:The rate constant and product rotational polarization

A quasi-classical trajectory(QCT) calculation is used to investigate the vector and scalar properties of the D + Br O → DBr + O reaction based on an ab initio potential energy surface(X1A state) with collision energy ranging from 0.1 kcal/mol to 6 kcal/mol. The reaction probability, the cross section, and the rate constant are studied. The probability and the cross section show decreasing behaviors as the collision energy increases. The distribution of the rate constant indicates that the reaction favorably occurs in a relatively low-temperature region(T 100 K). Meanwhile, three product angular distributions P(θr), P(φr), and P(θr, φr) are presented, which reflect the positive effect on the rotational angular momentum j' polarization of the DBr product molecule. In addition, two of the polarization-dependent generalized differential cross sections(PDDCSs), PDDCS00 and PDDCS20, are computed as well. Our results demonstrate that both vector and scalar properties have strong energy dependence.     

Theoretical study of stereodynamics for reaction O(3P)+HCl

<正>The vector correlation between products and reagents for reaction O(~3P)+HCl→OH+Cl is studied using a quasiclassical trajectory(QCT) method on the benchmark potential energy surface of the ground ~3A" state[Ramachandran and Peterson,J.Chem.Phys.119(2003)9550].The generalised differential cross section(2π/σ)(dσ_(00)/dω_t) is presented in the centre of mass frame.The distribution of dihedral angles,P(φr),and the distribution of angles between k and j', P(θ_r),are calculated.The influence of the collision energy and the influence of the reagent rotation and vibration on the product polarization are studied in the present work.The calculated results indicate that the rotational polarization of the product molecule is almost independent of collision energy but sensitive to the reagent rotation and vibration.     

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.     

Quasi-classical trajectory study of collision energy effect on the stereodynamics of H + Br O → O + HBr reaction

Quasi-classical trajectory(QCT) studies on the stereodynamics of H + Br O → O + HBr reaction have been performed on the X1A′state of ab initio potential energy surface by Peterson [Peterson K A 2000 J. Chem. Phys. 113 4598] in a collision energy range from 0 kcal/mol to 6 kcal/mol. Two of the polarization-dependent generalized differential cross sections(PDDCSs),(2π /σ)( dσ00/ dωt)(PDDCS00) and(2π /σ)( dσ20/ dωt)(PDDCS20) are considered. The rotational polarizations of these products show sensitive behaviors to the calculated collision energy range. Furthermore, in order to gain more knowledge about vector correlations, the product angular distribution, P(θr), and the dihedral angle, P(φr),are calculated, and the results indicate that both the rotational alignment and orientation of the product are enhanced as collision energy increases.     

A theoretical study of the stereodynamics on the abstraction reactions H/D ＋ HS/DS

The quasi-classical trajectory(QCT) method is employed to calculate the stereodynamics of the abstraction reactions H/D+HS/DS based on an accurate potential energy surface [L S J,Zhang P Y,Han K L and He G Z 2012 J.Chem.Phys.136 094308].The reaction cross sections of the title reaction are computed,and the vector correlations for different collision energies and different initial vibrational states are presented.The influences of the collision energy and reagent vibration on the product polarization are studied,and the product polarizations of the title reactions are found to be distinctly different,which arises from the different mass factors,collision energies,and reagent vibrational states.     

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.     

Theoretical study of stereodynamics for the D'+ DS(v=0,j=0) → D'D + S abstraction reaction

Quasiclassical trajectory (QCT) calculations have been performed for the abstraction reaction, D'+ DS(v = 0, j = 0) → D'D + S on a new LZHH potential energy surface (PES) of the adiabatic 3 A electronic state [Lü et al. 2012 J. Chem. Phys. 136 094308]. The collision energy effect on the integral cross section and product polarization are studied over a wide collision energy range from 0.1 to 2.0 eV. The cross sections calculated by the QCT procedure are in good accordance with previous quantum wave packet results. The three angular distribution functions, P(θr), P(φr), and P(θr,φr), together with the four commonly used polarization-dependent differential cross sections ((2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), (2π/σ)(dσ21/dωt)) are obtained to gain insight into the chemical stereodynamics of the title reaction. Influences of the collision energy on the product polarization are exhibited and discussed.