SPECTRAL DEPENDENCE OF RELAXATION IN YBA2CU3O7-DELTA WITH FEMTOSECONDLASER EXCITATION

A spectral dependence of the energy relaxation time of nonequilibrium charge carriers was determined by means of time measurements of the op tical density of a YBa2Cu3O7-delta film with the help of femtosecond l aser spectroscopy. The energy relaxation time increases rapidly in the spectral range corresponding to transitions into the vicinity of the Fermi level, This provides a new method for determining the position o f the Fermi level, Excitation of coherent phonons with frequencies in the range 10-250 cm(-1) was observed in a wide spectral probe range <( h)over bar omega>(probe) 1.6-3.0 eV. (C) 1995 American Institute of Ph ysics.