THE JOSEPHSON PLASMA MODE IN BI2SR2CACU2O8 AND QUASI-PARTICLE MEAN-FREE-PATH IN YBA2CU6O7

The Josephson plasma mode has been observed directly in Bi2Sr2CaCu2O8 using microwave radiation in the 30 to 90 GHz range. Measurements in a n oblique field provide firm evidence for the plasma oscillations, as well as a determination of the anisotropy parameter gamma. In a second experiment, we discuss how the mean free path l(0) of quasi-particles may be measured using asymmetric scattering off pinned vortices. In 9 0 K YBa2Cu3O7, we find that l(0) increases rapidly from 90 Angstrom at 100 K to 2500 Angstrom at 15 K.