Coherent Control of the Angular Distribution of Electrons Photoemitted from Metal Surfaces

We demonstrate that the angular distribution of electrons photoemitted from image states on a clean metal surface depends on the energies associated with the final electronic motion normal, $E_z$, and parallel, $E_{\Vert }$, to the surface. The surface normal $\hat{z}$ is the most probable direction of ionization when $E_z\gg E_{\Vert }$. But, for $E_z\approx E_{\Vert }$, many electrons are ejected away from $\hat{z}$ and the pattern of emission is altered dramatically. If a pump laser pulse produces a superposition of two image states, then the intensity and in certain cases the direction of photoemission from this wave packet can be coherently controlled via a probe pulse.