The direct-transition photoemission peak from the sp valence band of A
g(lll) shows a pronounced asymmetry. The emission intensity on the low
er binding energy side of this peak is considerably higher, and extend
s to a cutoff at the band edge just below the Fermi level. This extra
emission is derived from indirect transitions induced by the surface.
A linear combination of the direct (bulk) and indirect (surface) chann
els results in the asymmetric line shape.