The influence of the matrix element on angle-resolved photoemission spectra of insulating cuprates

Microscopic model calculations of the matrix element of a dipole moment are carried out in terms of the cluster model. This matrix element determines the transition probability of electron photoemission from a one-electron or bital with symmetry gamma mu to a free state. The effect of the matrix elem ent on the angular and polarization dependences in the angle-resolved photo emission spectra of insulating cuprates, such as Sr2CuO2Cl2 and Ca2CuO2Cl2, is analyzed under the assumption of a well-isolated ground state of the tw o-hole CuO45- cluster, namely, the Zhang-Rice singlet. The angular k depend ence of the matrix element gives rise to effects, such as the residual Ferm i surface, which are typical of metallic systems. An analysis of the experi mental data reveals the presence of another electronic state (with differen t symmetry) in the vicinity of the Zhang-Rice singlet. (C) 2001 MAIK "Nauka /Interperiodica".