Cu L3,2 and Ba M4,5 electro-optic effects in 50 nm YBa2Cu3O7 (YBCO) films on SrTiO3 (STO) bi-crystals with a 24 DEG ab-grain boundary*

. Two different films prepared at the Complutense University with a superconducting transition temperature T$_{c}$ = 90 $\pm $ 1 K, and characterized by X-ray diffraction at SSRL were investigated at station 6.3.1 of LBNL-ALS by enhanced YBCO 001 scattering (I$_{s})$, total electron yield (TEY) and fluorescence (F) at the Cu L$_{2,3}$ and Ba M$_{4,5}$ edges. The energy scale was calibrated by the Ti L$_{2,3}$ absorption from the spectrometer mirror, and the line shapes/intensities were checked using BaBr$_{2}$ and CuO standard references. The penetration depths at these energies ensure that the sample bulk dominated the F and I$_{s}$ signals. Comparison of I$_{s}$/I$_{0}$ with TEY/I$_{0}$ and F/I$_{0}$ indicates that the scattered linearly polarized light undergoes a rotation. The Hilbert-Kramers-Kronig analysis of F/I$_{0}$ and I$_{s}$/I$_{0}$ with Lorentzian line shapes of an eV width indicate extra absorption one eV above the L$_{3}$ edge that may be due to excitons.