^{1,a)}and Jose C. Corchado

^{2,b)}

### Abstract

Initial state-selected time-dependent wave packet dynamics calculations have been performed for the reaction using a seven-dimensional model and an analytical potential energy surface based on the one developed by Corchado and Espinosa-Garcia [J. Chem. Phys.106, 4013 (1997)]. The model assumes that the two spectator NH bonds are fixed at their equilibrium values. The total reaction probabilities are calculated for the initial ground and seven excited states of with total angular momentum . The converged cross sections for the reaction are also reported for these initial states. Thermal rate constants are calculated for the temperature range and compared with transition state theory results and the available experimental data. The study shows that (a) the total reaction probabilities are overall very small, (b) the symmetric and asymmetric NH stretch excitations enhance the reaction significantly and almost all of the excited energy deposited was used to reduce the reaction threshold, (c) the excitation of the umbrella and bending motion have a smaller contribution to the enhancement of reactivity, (d) the main contribution to the thermal rate constants is thought to come from the ground state at low temperatures and from the stretch excited states at high temperatures, and (e) the calculated thermal rate constants are three to ten times smaller than the experimental data and transition state theory results.

One of the authors (M.Y.) acknowledges support by the National Natural Science Foundation of China (No. 20403029). Another author (J.C.C.) acknowledges support by the Dirección General de Investigación Científica y Técnica of the Spanish Ministerio de Educación y Ciencia (CTQ2004-05680).

I. INTRODUCTION

II. THEORY

A. The coordinate system of

B. The kinetic Hamiltonian for group

C. The model Hamiltonian

D. Rotational basis set for the system

E. Wave function expansion and initial state wave function construction

F. Wave function propagation and reaction flux calculation

III. POTENTIAL ENERGY SURFACE

IV. RESULTS

A. Basis set

B. Total reaction probabilities

C. Integral cross sections

D. Rate constants

V. CONCLUSIONS

### Key Topics

- Reaction rate constants
- 43.0
- Hydrogen reactions
- 25.0
- Transition state theory
- 25.0
- Excited states
- 17.0
- Excited state reaction dynamics
- 16.0

## Figures

Jacobi coordinates of the model for reaction.

Jacobi coordinates of the model for reaction.

Potential energy along the ammonia inversion path. The abscissa axis shows the deviation from planarity of the molecule, and the zero of energy is set to the minimum geometry structure of ammonia. Dashed line: potential energy surface from Ref. 48 with the term; solid line: potential energy surface from Ref. 48 without the term; and dotted line: potential energy surface from Ref. 59.

Potential energy along the ammonia inversion path. The abscissa axis shows the deviation from planarity of the molecule, and the zero of energy is set to the minimum geometry structure of ammonia. Dashed line: potential energy surface from Ref. 48 with the term; solid line: potential energy surface from Ref. 48 without the term; and dotted line: potential energy surface from Ref. 59.

(a) Total reaction probability for the reaction from the eight initial states as a function of translational energy. (b) Same as (a) except plotted as a function of total energy.

(a) Total reaction probability for the reaction from the eight initial states as a function of translational energy. (b) Same as (a) except plotted as a function of total energy.

(a) Integral cross sections for the reaction from the eight initial states as a function of translational energy. (b) Same as (a) except plotted as a function of total energy.

(a) Integral cross sections for the reaction from the eight initial states as a function of translational energy. (b) Same as (a) except plotted as a function of total energy.

(a) Arrhenius plot of the TST thermal rate constants and TDWP thermal and initial state-selected rate constants. (b) Arrhenius plot of the TST thermal rate constants and TDWP thermal and initial state-selected rate constants for high temperature.

(a) Arrhenius plot of the TST thermal rate constants and TDWP thermal and initial state-selected rate constants. (b) Arrhenius plot of the TST thermal rate constants and TDWP thermal and initial state-selected rate constants for high temperature.

## Tables

Vibrational frequencies and changes in potential energy of the reactants, products, and saddle point of the hydrogen abstraction reaction reaction computed using the potential energy surface from Ref. 48 with and without the term.

Vibrational frequencies and changes in potential energy of the reactants, products, and saddle point of the hydrogen abstraction reaction reaction computed using the potential energy surface from Ref. 48 with and without the term.

Semiclassical small-curvature tunneling factors computed using the potential energy surface from Ref. 48 with and without the term.

Semiclassical small-curvature tunneling factors computed using the potential energy surface from Ref. 48 with and without the term.

Thermal rate constant for the reaction, in . The TST rate constant are computed using the potential energy surface from Ref. 48 with and without the term. The QCT and TDWP thermal rate constant are computed using the potential erergy surface without the term. Experimental rate constant from Ref. 66.

Thermal rate constant for the reaction, in . The TST rate constant are computed using the potential energy surface from Ref. 48 with and without the term. The QCT and TDWP thermal rate constant are computed using the potential erergy surface without the term. Experimental rate constant from Ref. 66.

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