Importance of matrix elements in the ARPES spectra of BISCO

We have carried out extensive first-principles angle-resolved photointensit y (ARPES) simulations in Bi2212 wherein the photoemission process is modele d realistically by taking into account the full crystal wave functions of t he initial and final states in the presence of the surface. The spectral we ight of the ARPES feature associated with the CuO2 plane bands is found to undergo large and systematic variations with k(\\) as well as the energy an d polarization of the incident photons. These theoretical predictions are i n good accord with the corresponding measurements, indicating that the rema rkable observed changes in the spectral weights in Bi2212 are essentially a matrix element effect and that the importance of matrix elements should be kept in mind in analyzing the ARPES spectra in the high T-c's.