Harmonics generation and chaos in scattering of phonons from anharmonic surfaces

The effective equations of motion for a surface atom in an anharmonic surface potential have been derived for dispersionless one-dimensional substrates. The system is equivalent to a non-linear damped oscillator (Duffing oscillator) with the forcing term depending on the form of the incident wave. Efficiency of harmonics generation, phonon reflection coefficients, effective local density of states, regions of chaotic motion and windows of periodic motion have been comparatively evaluated for the system subject to an oscillating external force and to the irradiation by a monochromatic phonon coming from the bulk. Comparison of the resonant desorption of the surface atom within a given time interval has been made for the same example of anharmonic surface potential in both types of perturbation. Received 9 November 1998