A Reactant-Coordinate-Based Time-Dependent Wave Packet Method for Triatomic State-to-State Reaction Dynamics: Application to the H + O₂ Reaction

Abstract

A new time-dependent wavepacket method is developed to study the A + BC --> AB + C, AC + B reaction at the state-to-state level. The method only requires propagation of the wavepacket in reactant Jacobi coordinates by extracting S-matrix information on a dividing surface right before the absorption potential in the product region. It has particular advantages for reactions with deep wells and long-range attractive interactions in the product channels in which the wavepacket in the product channels can only be absorbed sufficiently far away from the interaction potential. Demonstration made on the benchmark H + H(2) reaction shows that the method is rather efficient in dealing with a direct reaction at high collision energy. The method is applied to study the very challenging H + O(2) (nu(0) = 0, j(0) = 0, 1) reaction, with state-to-state differential cross sections obtained for the first time for collision energies up to 1.1 eV. The calculations not only show the power and accuracy of the new approach in dealing with complex-forming reactions but also shed light on the dynamics of the H + O(2) reaction.

Extraction of state-to-state reactive scattering attributes from wave packet in reactant Jacobi coordinates

“…In this work, the propagation of the wave packet is carried out exclusively in reactant Jacobi coordinates 20,22 in the BF frame using the Chebyshev real wave packet ͑CRWP͒ approach. 15,28,29,32,33 The corresponding Hamiltonian for a given total angular momentum J can be written as…”

“…A direct product discrete variable representation ͑DVR͒ is used for the two radial degrees of freedom and a finite basis representation ͑FBR͒ of spherical harmonics basis y jK ͑ ␣ ͒ is used for the angular degree of freedom. 34 Thus the wave function in the BF frame can be written as 20,[35][36][37][38] …”

“…[20][21][22][23] Taking advantage of a L-shaped grid to propagate in reactant coordinates, this collocation method is efficient and accurate and has been successfully applied to calculate state-to-state DCSs for the H+HD, F+H 2 , H + NH, H + ND, 24 H+O 2 , 20,21 and O + O 2 reactions. 25 The L-shaped grid method saves a large number of grid points, as compared with a conventional rectangular grid, which makes this RCB wave packet method particularly attractive and presents an efficient alternative to the PCB approaches.…”

“…In this paper, we first compare the two RCB wave packet methods, introduced by us 20 and by Gómez-Carrasco and Roncero, 26 for studying the A + BC→ AB+ C, AC+ B type reaction at the state-to-state level, using the H + HD reaction as an example. These RCB methods were implemented with the efficient and accurate Chebyshev propagator.…”

“…These RCB methods were implemented with the efficient and accurate Chebyshev propagator. [28][29][30] It is shown that the coordinate transform RCB method can also be used to extract S-matrix elements in both product channels with a single propagation, as the RCB method introduced by us 20,22 and it is generally more efficient. The two RCB methods were then applied to the Cl+ H 2 reaction to demonstrate the advantages of a L-shaped grid.…”