Interference of direct transitions and surface emission in ARPES studied by changing the light incidence angle

The contributions of direct transitions [f\(A) over right arrow.(p) over ri ght arrow \i] and surface emission [f\div (A) over right arrow \i] in angle -resolved photoelectron spectroscopy spectra can be varied considerably by changing the incidence angle of p-polarized light. Due to interference of b oth contributions line shape and asymmetry of certain peaks change dramatic ally as a function of light incidence direction. This effect has been studi ed in detail at an s.p band of copper and a photon energy of h omega =21.2 eV. Our experimental data can be explained quantitatively within a physical ly transparent model calculation, which supplies a criterion to distinguish between bulk direct and surface emission.