The role of vibrational excitation of a single mode in the scattering of methane is studied by wave packet simulations of oriented ${\mathrm{CH}}_4$ and ${\mathrm{CD}}_4$ molecules from a flat surface. All nine internal vibrations are included. In the translational energy range from 32 up to 128 kJ/mol we find that initial vibrational excitations enhance the transfer of translational energy towards vibrational energy and increase the accessibility of the entrance channel for dissociation. Our simulations predict that initial vibrational excitations of the asymmetrical stretch $\left({\nu }_3\right)$ and especially the symmetrical stretch $\left({\nu }_1\right)$ modes will give the highest enhancement of the dissociation probability of methane.

• Received 25 February 2000

DOI:https://doi.org/10.1103/PhysRevB.61.15657