COUPLED-CHANNEL APPROACH TO MOLECULAR VIBRATION DYNAMICS IN MOLECULE SURFACE INTERACTIONS

We propose an accurate and numerically stable coupled channel approach to molecular vibration dynamics in diatomic molecule-surface interactions. This approach successfully avoids the triple-valued problem of the conventional reaction path coordinate system by using a widely curved path that defines the curvilinear coordinates. The degree of the coordinate error is found to depend on the curvature of the path, the vibrational wavelength, and the molecular energy, which determine the spread of the wavefunction. We discuss when and by how much the path should be shifted, by giving an example of H-2/Cu dissociative adsorption. Also, changes in the molecular vibrational frequency are correctly included in a straightforward way. Numerical stability in computing the coupled equations is achieved by introducing a local reflection matrix, which is closely related to the logarithmic derivative of the solution matrix.