  Recently, the intrinsic sampling method has been developed in order to
obtain, from molecular simulations, the intrinsic structure of the liquid-vapor
interface that is presupposed in the classical capillary wave theory. Our
purpose here is to study dynamical processes at the liquid-vapor interface,
since this method allows tracking down and analyzing the movement of surface
molecules, thus providing, with great accuracy, dynamical information on
molecules that are "at" the interface. We present results for the coefficients
for diffusion parallel and perpendicular to the liquid-vapor interface of the
Lennard-Jones fluid, as well as other time and length parameters that
characterize the diffusion process in this system. We also obtain statistics of
permanence and residence time. The generality of our results is tested by
varying the system size and the temperature; for the later case, an existing
model for alkali metals is also considered. Our main conclusion is that, even
if diffusion coefficients can still be computed, the turnover processes, by
which molecules enter and leave the intrinsic surface, are as important as
diffusion. For example, the typical time required for a molecule to traverse a
molecular diameter is very similar to its residence time at the surface.
