Momentum-resolved excited-electron lifetimes on stepped Cu(7 7 5)

The lifetime of n=1 image-state electrons on stepped on Cu(7 7 5) has been measured as a function of their translational momentum, k∥. At the terrace normal this lifetime is equal to that for flat Cu(1 1 1), i.e. τ=18±2 fs. For motion parallel to the step orientation, the lifetime decreases symmetrically about k∥=0 and the absolute values are in close agreement with that predicted by a recent many-body theory. Contrasting data for motion perpendicular to the step edges is also presented.