Polarization-dependent Differential Cross Sections Research Articles

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)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), (2π/σ)(dσ21−/dωt) and the distributions of P(θr), 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.

Reaction Dynamics and Mechanism of the Cl + HD(v = 1) Reaction: A Quantum Mechanical Study

Time-independent quantum mechanical calculations have been performed in order to characterize the dynamics and stereodynamics of Cl + HD reactive collisions. Calculations have been carried out at two different total energy values and for various initial states using the adiabatic potential energy surface by Bian and Werner [J. Chem. Phys. 2000, 112, 220]. Special attention has been paid to the reaction with HD(v = 1) for which integral and differential cross-sections have been calculated and the effect of vibrational vs translational energy on the reactivity has been examined. In addition, the reactant polarization parameters and polarization-dependent differential cross-sections have been determined. From these results, the spatial preferences of the reaction and the extent of the control of the cross sections achievable through a suitable preparation of the reactants have been also studied. The directional requirements are tighter for the HCl channel than for the DCl one. Formation of the products takes place preferentially when the rotational angular momentum of the HD molecule is perpendicular to the reactants approach direction. Cross-sections and polarization moments computed from the scattering calculations have been compared with experimental results by Kandel et al. [J. Chem. Phys. 2000, 112, 670] for the reaction with HD(v = 1) produced by stimulated Raman pumping. The agreement so obtained is good, and it improves the accordance found in previous calculations with other methodologies and potential energy surfaces.

Rotational alignment effects in NO(X) + Ar inelastic collisions: An experimental study

Rotational angular momentum alignment effects in the rotationally inelastic collisions of NO(X) with Ar have been investigated at a collision energy of 66 meV by means of hexapole electric field initial state selection coupled with velocity-map ion imaging final state detection. The fully quantum state resolved second rank renormalized polarization dependent differential cross sections determined experimentally are reported for a selection of spin-orbit conserving and changing transitions for the first time. The results are compared with the findings of previous theoretical investigations, and in particular with the results of exact quantum mechanical scattering calculations. The agreement between experiment and theory is generally found to be good throughout the entire scattering angle range. The results reveal that the hard shell nature of the interaction potential is predominantly responsible for the rotational alignment of the NO(X) upon collision with Ar.

THEORETICAL STUDY OF THE STEREODYNAMICS OF THE N(4S) + D2 → ND + D REACTION ON THE DMBE SURFACE

Utilizing the quasiclassical trajectory method, the product rotational polarization of the reaction N(4S) + D2 → ND + D has been calculated at different collision energies on the DMBE potential energy surface [Poveda LA et al., Phys Chem Chem Phys7:2867, 2005]. The distribution of the angle between k and j′, P(θr), the distribution of dihedral angle denoting k–k′–j′ correlation, P(ϕr), as well as the angular distribution of product rotational vectors in the form of polar plots P(θr, ϕr) are calculated. In addition, the four commonly used polarization-dependent differential cross sections, dσ00/dωt, dσ20/dωt, dσ22+/dωt, and dσ21-/dωt with ωt being the polar coordinates of the product velocity k′, are calculated in the center-of-mass frame. The effects of the collision energy on the product polarization are presented and discussed. In comparison with the result of Yu et al. [Yu YJ et al., Chin Phys B20:123402, 2011], significant isotope effects on the stereodynamics of N(4S) + D2(H2) → ND(H) + D(H) have also been revealed.

Influence of collision energy and reagent vibrational excitation on the stereodynamics of the reaction H + LiH → H2 + Li

Quasi-classical trajectory calculations have been carried out to investigate the stereodynamics of the reaction H+LiH→H2+Li which proceeds on the ground electronic state of LiH2 system, using a recent potential energy surface of Prudente et al. The effects of collision energy and reagent vibrational excitation on the product polarization are studied for the ν=0–3, j=0 states of LiH over a wide collision energy range. It has been found that the collision energy and the vibrational excitation of the reagent remarkably influence the four generalized polarization-dependent differential cross-sections, the distributions of P(θr), P(ϕr), and P(θr,ϕr). The calculated results show that the rotational angular momentum j′ of the product H2 is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The orientation of j′ depends very sensitively on the collision energy and the vibrational excitation of the reagent.

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) → H+2+Ne is studied theoretically with a quasi-classical trajectory method on a new ab initio potential energy surface [Lü 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 polarization-dependent 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.

Stereodynamics study of Li+HF (v = 0–3,j = 0)→LiF+H reaction

The detailed stereodynamics of the reaction Li+HF(v=0–3) with different collision energy and in different vibration-excited state has been carried out by using the quasi-classical trajectory (QCT) method based on a new potential energy surface constructed by Aguado and Pariagua (Aguado and Paniagua J. Chem. Phys., Vol. 119, No. 19, 2003). The correlated k-j', k-k'-j' angular distributions and the polarization-dependent differential cross sections (PDDCSs) are discussed in detail. The results indicate that the collision energy has more impact on the P(θr) distributions describing the k-j' correlation than the vibration excitation. The distributions of P(φr) describing the k-k'-j' correlation, as well as the polarization-dependent generalized differential cross-sections, are sensitive to the vibration excitation. Meanwhile, the collision energy also has more influence on them.

Quasi-Classical Trajectory Study of the Reaction N(4S) + H2 (v = 0, j = 0) → NH + H(2S) Stereo Dynamics Properties

Using a quasi-classical trajectory study method, the stereodynamics for N(4S) + H2 (v = 0, j = 0) → NH + H(2S) reaction have been investigated on an accurate NH2 potential energy surface (PES) reported by Poveda and Varandas [L. A. Poveda, A. J. C. Varandas, Phys. Chem. Chem. Phys. 7(2005)2867], in the collision energy range of 25–70 kcal mol−1. The four generalized polarization dependent differential cross-sections (PDDCSs) (2π/σ)(dσ00/dω t ), (2π/σ)(dσ20/dω t ), (2π/σ)(dσ22+/dω t ), (2π/σ)(dσ21−/dω t ) and the rotational-state distributions of product NH are calculated in the center-of-mass frame at three different collision energies. The distribution of the angle between k ′ and j′, P(θ r ), the distribution of the dihedral angle denoting k - k ′- j ′ correlation, P(φ r ), as well as the angular distribution of product rotational vectors in the form of polar plots P(θ r , φ r ) are discussed. The results indicate that the product rotational angular momentum j ′ is not only aligned, but also oriented along the negative direction of y-axis. The calculated results reveal that the stereo-dynamics properties of the title reactions are sensitive to the collision energy.

QUASICLASSICAL TRAJECTORY STUDY OF PRODUCT POLARIZATIONS IN THEH(2S) +NH→N(4S) +H2REACTION

Based on the DMBE potential surface of the4A ″ ground-state, the product rotational polarizations in the title reaction are studied by using quasiclassical trajectory (QCT) calculation method. Three angular distributions of P(θr), P(Φr), P(θr, Φr) and the four polarization-dependent differential cross sections (PDDCSs) were calculated for the collision energy range of 1–20 kcal/mol. The results revealed that the product is backward-scattering and the product rotational angular momentum j′ is aligned and oriented. With the increment of collision energy, the degree of the product alignment and orientation is enhanced, showing the collision energy-dependent behaviors of the product polarizations.

VECTOR CORRELATIONS AND PRODUCT POLARIZATIONS IN THE N(2D) + D2 → ND + D REACTIVE SYSTEM

The vector correlations between products and reagents of the N (2D) + D 2 reaction are investigated by employing quasi-classical trajectory (QCT) calculation on the accurate DMBE potential energy surface (PES) of the 2A″ state. Stereo-dynamic quantities, including the four generalized polarization-dependent differential cross-sections (PDDCSs), the angular distribution P(θr), the dihedral-angle distribution P(φr), as well as the product rotational angular distribution in the polar form of P(θr, φr), are calculated in the center-of-mass (CM) frame. The results indicate that the product rotational angular momentum j′ not only aligns along the y-axis, but also orients to the negative direction of the y-axis. The isotope effect in the context of chemical stereo-dynamics and influences of different versions of ground-state PESs on vector correlations are shown and discussed.

Product rotational angular momentum polarization in the N + NH (v = 0, j = 0, 3, 6, 9)→N2 + H reaction

Based on the ground state HN2(12A′) potential energy surface (PES), the effects of collision energy and the rotational excitation of the reagent on the product alignment and the orientation for the title reaction are investigated by using quasi-classical trajectory (QCT) method. The distribution of polar angle P(θr) at collision energies 2–40kcal/mol with v=0 and j=0 level has been presented. The three angle distribution functions P(θr), P(ϕr), P(θr,ϕr) and four generalized polarization dependent differential cross sections (PDDCSs) at collision energy of 10kcal/mol with different rotational excitation are plotted. The results show that the product rotational angular momentum j′ is not only aligned, but also oriented along the direction perpendicular to the scattering plane. It has been found that the three angle distributions are sensitive to initially rotational excitation. The HHL mass combination and the property of the PES are used to explain the found results.

Effects of a reagent's rotational and vibrational excitations on reaction O(3P) + H2(ν = 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 3A″ and 3A′ 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.

INFLUENCE OF VIBRATIONAL EXCITATION AND COLLISION ENERGY ON THE STEREO DYNAMICS OF THE REACTIONS:N(4S)+H2(v = 0-3,j = 0) →NH(X3Σ-)+H

Quasi-classical trajectory (QCT) calculations have been carried out to study the stereodynamics of the title reactions, using the double many-body expansion (DMBE) potential energy surface (PES) constructed by Poveda [Poveda LA, Varandas AJC, Phys. Chem. Chem. Phys.7:2867, 2005]. Vector correlations, such as the distributions of the polarization-dependent differential cross-sections (PDDCSs), the angular distributions of P(θr), P(ϕr), P(θr,ϕr), and the product alignment parameter P2( cos θr) are reported within the energy range of 25–140 kcal mol-1. The influences of the collision energy and the initial state-selected vibrational excitation are discussed in detail. In addition, Validity of the current QCT calculations is also examined and compared with the revelant results reported by Pascual et al. [Pascual RZ, Schatz GC, Lendvay G, Troya D, J. Phys. Chem. Aਠ106:4125, 2002].

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

Stereodynamics for the reaction H+LiF(ν = 0, j = 0) → HF+Li and its isotopic variants on the ground-state (12A′) 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 PDDCS00 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.

A QUASI-CLASSICAL TRAJECTORY STUDY ON STEREODYNAMICS OF THEF+HCl(v = 0, j = 0) →HF+ClREACTION

Quasiclassical trajectory (QCT) calculations for the title reaction are carried out by employing the recent developed accurate potential energy surface of the 12A′ ground state. Two angular distributions, P(θr) and P(ϕr), with θr, ϕrbeing the polar angles of the product angular momentum, and two commonly used polarization dependent differential cross sections, (2π/σ)(dσ00/dωt) and (2π/σ)(dσ20/dωt), with ωtbeing the polar coordinates of the product velocity, are generated in the center-of-mass frame. It was found that the product rotational angular momentum j′ is not only aligned, but also oriented along the negative direction of y-axis. We also investigated the product state distributions in the present work, and found that the vibrational and rotational state distributions are inverted. Influences of collision energies on the product polarization and state distributions are also shown and discussed.

EFFECTS ON THE CHEMICAL STEREODYNAMICS OF THE INITIAL VIBRATIONAL EXCITATION IN THEF+LiH(v = 0-2, j = 0) →LiF+HREACTION

In this work, the product polarization characteristics are reported for the reaction F + LiH (v = 0 - 2, j = 0) → LiF + H at the collision energy of 35 kcal/mol, by using the QCT method on the Aguado–Paniagua-potential energy surface (see Aguado et al.). The distribution of P(θr) which represents the K (reagent relative velocity vector) and J′ (product rotational angular momentum vector) correlation, the dihedral angle distribution of K-K′ (product relative velocity vector)-J′ P(φr), the angular distribution P(θr, φr) and the four polarization-dependent differential cross sections (2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), (2π/σ)(dσ21-/dωt) in each initial state are presented and discussed.

Influence of collision energy on cross section and stereodynamical properties for the reaction H + OCl → OH + Cl

The quasi-classical trajectory calculations are carried out for the reaction H+OCl→OH+Cl on the singlet ground state potential energy surface. The reaction probability for total angular momentum J=0 and the integral cross section as a function of collision energy are presented. Furthermore, the product rotational alignment <P2(j′·k)> has been obtained, and the value tends to decrease with the increasing of collision energy with fluctuations. To investigate the collision-energy-dependent effects on chemical stereodynamics, the four generalized polarization-dependent differential cross sections (2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt) and (2π/σ)(dσ21−/dωt), the distribution P(θr) of the angle between j′–k and the angle distribution P(ϕr) in terms of k–k′–j′ correlation have also been calculated.

Stereodynamics of the reactions Ne+H+2/Ne+D+2/Ne+T2

The vector correlations between products and reagents for the reactions Ne+H+2, Ne+D+2, and Ne+T+2 are calculated by means of the quasi-classical trajectory method on a new potential energy surface constructed by Lü et al. [J. Chem. Phys. 2010 132, 014303]. The polarization-dependent differential cross-sections (2π/σ)(dσ00/dωt), (2π/σ)(dσ20/dωt), (2π/σ)(dσ22+/dωt), and (2π/σ)(dσ21−/dωt), and the distributions of P(θr), P(φr), and P(θr, φr) are calculated. The isotopic effect, which is associated with the difference in mass factor among the three reactions, is revealed.

Stereodynamics study of the O+ + D2 (υ = 0, j = 0–2) → OD+ + D reaction

The vector correlations between products and reagents for the ion–molecule reaction O+ + D2 → OD+ + D with different rotational quantum numbers (j = 0, 1, or 2) were explored theoretically using the quasi-classical trajectory method (QCT) on a Martìnez–Millán–González (MMG) surface. The three angular distributions P(θr), P([Formula: see text]), and P(θr,[Formula: see text]), as well as four polarization-dependent differential cross sections (PDDCSs) were calculated. The results indicate that a reagent’s rotational excitation greatly influences both the vector correlations of k–k′, k–j′, and k–k′–j′ and the PDDCSs of the title reaction, which means the reactivity is very sensitive to the rotational quantum number.

A detailed study on stereodynamics of He+H2 +(v=1, j=1) reaction with quasi-classical trajectory calculations

Calculations of He+H2+ (v=1, j=1) reaction system are carried out on a new potential energy surface (PES) at different collision energies with the quasi-classical trajectory (QCT) method. The results of the reaction probability and the cross section curves show an obvious oscillatory structure attributed to the resonances caused by the potential well of the HeH2+ complex. The three angular distributions P(θr), P(ϕr) and P(θr, ϕr) as well as four polarization dependent differential cross sections (PDDCSs) are calculated, respectively. Results indicate that the collision energy has great influence on both the vector correlation of k-k′, k-j′, k-k′-j′ and the PDDCSs of the title reaction. The rotational polarization of product HeH+ presents diverse characteristics at different collision energies. The rotational angular momentum vectors j′ of product are both aligned and oriented. Furthermore, the product HeH+ tends to scatter forward correspondingly as the collision energy increases.