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[en] The report deals with the effects of superconducting fluctuations (S F) on the 63 Cu NQR-NMR relaxation rate in YBCO as studied from a careful comparison of measurements carried out in the absence and in the presence of a field parallel to the c-axis in an oriented powder sample. The application of a magnetic field is observed to cause the reduction of the relaxation rate W in a range of about 10 K above Tc. This effect is related to the suppression by the magnetic field of the phase-sensitive positive Maki-Thompson contribution which allows one to evidence the decrease in W due to the reduction of the one-electron density of state. It is argued how the fluctuation effects on W can be used to discuss the pairing state symmetry, at variance with the insensitivity of the transport measurements. It is pointed out how the existence of the Maki-Thompson contribution to W supports an s-wave symmetry component for the pairing in YBCO
[en] In this paper, a recent combined isotope and interdiffusion analysis is adapted to the case of binary liquid alloys. Shear-cell interdiffusion experiments with a layer enriched in 65Cu sandwiched between the interdiffusion couple ends have been performed on liquid Al-Cu that is suitable for demonstration of the application of this analysis. (Note that the analysis is not limited to the use of the shear-cell technique.) The self-diffusion coefficient of Cu is then obtainable as a function of composition. Results of the new analysis are in good agreement with an independently measured Cu self (tracer) diffusion coefficient at two compositions.
[en] The lifetime of the first two excited state in Co59 and Cu65 and of the first three excited states in Cu63 have been measured by the Doppler Shift Attenuation Method (DSAM); the levels were Coulomb excited using a beam of oxygen ions from our Tandem Van de Graaff accelerator. (author)
[en] The properties of levels in 63Cu and 65Cu have been investigated using the resonance fluorescence technique with bremsstrahlung serving as the source of exciting radiation. The energies and scattering cross sections for 24 levels in 63Cu and 30 levels in 65Cu up to about 4.5 MeV were measured. A few levels known to exist in the region of 2 MeV for both nuclei were not observed. For a number of the lower lying levels, spin and parity assignments have been made through angular distribution measurements and limits on J/sup pi/ set by others. Mixing ratios for a few of these are also given. Where J/sup pi/ and the ground state branching ratios are known the partial widths for decays to the ground state are presented. Comparisons are made with the predictions of the latest theoretical calculations