LA-139 NMR-NQR STUDY OF THE OXYGEN DIFFUSION IN LA2-XSRXCUO4+DELTA

High-temperature (T > 200 K) La-139 NMR relaxation rates in single cry stals of La2CuO4+delta (delta similar to 0.015 and delta similar to 0. 002) at two measuring frequencies are presented and compared with zero -field NQR data for a series of La2-xSrxCuO4+delta powder samples with 0 less than or equal to x less than or equal to 0.08 and 0 < delta le ss than or equal to 0.013. For delta not equal 0 an enhancement of the relaxation rate is observed which is related to the time dependence o f the quadrupole interaction. Quantitative information on the oxygen d iffusion is obtained from the analysis of the data with a simple diffu sion model. The results are discussed in relation to the problem of ma croscopic phase separation occurring for higher oxygen content.