Product rotational angular momentum polarization of H+FCl (v=0-5; j=0, 3, 6, 9) → HF+Cl and HCl+F at Erel=0.5-20 kcal mol(-1)

The rotational angular momentum polarizations of product molecules of the title reactions on the ground potential energy surface 1 (2)A' of DHTSN [Deskevic et al. J Chem Phys 2006, 124, 224303] have been studied using the quasi-classical trajectory method. Reaction dynamic results of the HF product channel comparing with another channel of HCl with 100,000 trajectories can be accurately resolved. We show the value of the polar p(ϑr) in the range of 0° ≤ ϑr ≤ 180(°), azimuthal p(φr) in the range of 0° ≤ φr ≤ 360(°), and dihedral p(ϑr, φr) in the ranges of 0(°) ≤ ϑr ≤ 180(°) and 0(°) ≤ φr ≤ 360(°); the angular distributions of the product molecules HF and HCl at relative Erel = 0.5, 1, 2, 5, 10, 15, and 20 kcal mol(-1); and four polarization-dependent differential cross sections (PDDCSs) of HF and HCl at Erel = 0.5, 1, 2, 5, 10, and 15 kcal mol(-1). p(φr) distributions at v = 0-5, and j = 0, 3, 6, 9 at every Erel are plotted cylindrically together. The stereo dynamic transformation reaction dependent upon the rovibrational states of the reactant molecule FCl and its relative translational energies around 0.5-5 kcal mol(-1) can be significantly differentiated. Translational and rovibrational enhancements of the title reactions on both early barrier potential energy surfaces have been shown in great detail and clarified. Reaction mechanisms of forward and backward scattering of the product molecules HF and HCl, respectively, have been obtained. Graphical Abstract H + FCl → either HF + Cl (left) or HCl + F (right) is moving along a trajectory on the respective PES.

Reagent vibrational, rotational and isotopic effects on stereodynamics of the H + OCl → OH + Cl reaction

The quasi-classical trajectory method has been employed to investigate the initial vibrational and rotational effects of the title reaction on an improved ab initio potential energy surface for the 11A′ state. Meanwhile, isotopic effect has also been studied at collision energy of 19 kcal/mol. The product rotational alignment factor 〈P2(j′ • k)〉, angular distributions of P(ϕr), P(θr) and the generalized polarization dependent differential cross-sections have been calculated. The- results show that the reagent vibrational excitation generally strengthens the product alignment perpendicular to the reagent relative velocity vector k and affects the product scattering preference, and the rotational excitation has the same trend from j = 0 to 2 except for the higher excitation of j = 3. Further, the substitution of atom H with D leads to a stronger product alignment while changes some stereodynamical properties subtly.

SEVEN-DIMENSIONAL QUANTUM DYNAMICS STUDY OF THE H2 + NH2 → H + NH3 REACTION ON AN INTERPOLATED POTENTIAL ENERGY SURFACE

Initial-state-selected time-dependent wave packet dynamics studies have been performed for the H 2 + NH 2 → H + NH 3 reaction with a seven-dimensional model on a new interpolated ab initio potential energy surface (PES). The PES is constructed using modified Shepard interpolation Scheme and contains 1967 data points with ab initio calculations carried out on UCCSD(T)/aug-cc-pVTZ level. In the seven-dimensional model, NH 2 group keeps C2v symmetry and two NH bonds are fixed at their equilibrium values. The total reaction probabilities are calculated when (1) the two reactants are initially at their ground states; (2) NH 2 bending mode is excited, and (3) H 2 is on its first vibrational excited state. The integral cross sections are also reported for these initial states with centrifugal-sudden approximation. Thermal rate constants are calculated for the temperature range of 200–2000 K and compared with the previous calculated values and available experimental data. Good agreements between theory and experiments for the rate constants at intermediate temperature are achieved on this PES.

INVESTIGATION OF THE EXCHANGE REACTION H + H′S → HS + H′ ON THE 1A′ STATE POTENTIAL ENERGY SURFACE

The quantum time dependent wave packet (TDWP) and quasiclassical trajectory (QCT) calculations were carried out to study the exchange reaction H(2S) + H′S(2Π) → HS(2Π) + H′(2S) on the 1A′ potential energy surface (PES). The integral cross sections of the H + H′S (v = j = 0) → HS + H′ reaction calculated by the two methods were presented. The results reveal that the integral cross sections (ICS) decrease with the collision energy increasing. The result of the QCT calculations is reasonably consistent with the time-dependent wave packet. Moreover, the differential cross sections (DCS) were calculated by the QCT method at the four different collision energies, which display a forward–backward symmetry. A long-lifetime H2S intermediate complex of the exchange reaction was found according to the trajectories. In the stereodynamics investigation, the polar and dihedral angle distribution functions were calculated, which have the distinct oscillations. The oscillations could be attributed to the deep well on the 1A′ PES. However, based on the polar-angle and dihedral angle distribution functions, it could be predicted that the main product rotational angular momentum preferentially point to the positive or negative direction of y-axes.

QUASI-CLASSICAL TRAJECTORY STUDY OF THE REACTION N + NH (v = 0–3, j=0) → N2 + H

The quasi-classical trajectory (QCT) calculations have been carried out for the reaction N + NH (v = 0–3, j=0) → N2 + H on the ground state of double many-body expansion (DMBE) potential energy surface [Caridade, PJSB, Poveda LA, Rodrigues SPJ, Varandas AJC, J Phys Chem A111:1172, 2007]. The influence of reagent vibrational excitation on reaction probability for total angular momentum J = 0 and integral cross section (ICS) at collision energies ranging from 0.1 eV to 1.0 eV has been investigated. The reaction probability tends to decrease with increasing collision energy and increase with the rising of initial vibration state, although some fluctuations appear. The ICS declines monotonously with the increase of collision energy and v. The product rotational alignment factor 〈P2(j′•k)〉 has also been calculated, and its value has a declining trend with the increase of collision energy. In spite of that, the results still show that the product is highly aligned. In addition, the vibrational excitation effect on the product polarization has also been studied. All the distributions of P(ϕr), P(θr), and the generalized polarization dependent differential cross sections indicate dependent behaviors on v.