EXPERIMENTAL-ANALYSIS OF VALENCE-BAND PHOTOEMISSION INTENSITIES FOR CU(111) AND CU(100)

Angle-resolved photoemission with p-polarized He I radiation has been used to study transition matrix elements of bulk direct transitions in copper. From peak intensities as a function of light incidence angle the direction and relative magnitude of the momentum matrix element P- fi = [f\p\i] have been determined. At a fixed point in k space P-fi is independent of the special experimental geometry and depends only on the initial- and final-state wave function. Therefore it is particular ly suitable for comparison to theory. We present measurements of the m omentum matrix element for bulk transitions out of d- and sp-like band s. Selected k-space points have been triangulated from Cu(111) and Cu( 100) surfaces. Within the error bars direction and absolute value of P -fi are found to be independent of the particular surface. This shows that the description of the matrix element in terms of bulk direct int erband transitions may be a reasonable approximation in many cases. Mo reover these results demonstrate that the macroscopic Fresnel equation s are appropriate to describe the light properties inside the sample u nder the experimental conditions of our experiment. [S0163-1829(98)072 40-3].