CUO-CHAIN RAMAN-SCATTERING AND PHOTOINDUCED METASTABILITY IN YBA2CU3OX

Raman measurements in YBa2Cu3Ox (x=6.72-6.82) high-T-c superconductors reveal intense phonon scattering due to an electronic resonance local ized near oxygen vacancies on the CuO chains. Below room temperature t he resonance can be photobleached in a manner similar to reported pers istent photoinduced superconductivity effects, indicating photon-assis ted oxygen ordering or electron vacancy capture. By comparing Raman an d x-ray diffraction data we establish a correlation between the stabil ity of the photoinduced state and the oxygen-ordering kinetics in the CuO chains.