  A continuum (Mullins-type) model is formulated for the isotropic evolution of
a solid surface on which the mass transport occurs by oscillatory surface
diffusion. The time-space oscillations of diffusivity are assumed to be induced
by external source(s); a number of possible sources, different in their
physical nature has been suggested in \cite{P-LH}. The particular driving
mechanism assumed here is low-energy, pulsed electron or laser beam(s) incident
on a surface. The simplified version of the model is applied to study the
relaxation of a periodic surface corrugation. Several extensions of the model
are proposed.

Materials Science