Bound Hole States and Ferrons in Htsc Typeset Using Revt E X

Bound hole states induced by excess oxygen in La 2 CuO 4+ are studied in the framework of the extended Hubbard model, using the spin-wave approximation and the Lanczos algorithm. We interpret the band at 0:5 eV in the impurity reeectivity spectrum as connected with the transition from the lowest bound hole level (S z = 1=2) to the unperturbed hole band. It is shown that in the realistic parameter range the excess O 2? ion does not lead to the formation of ferrons. On the other hand the spin-carrying defect O ? can stabilize ferrons.