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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 T_c. 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

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[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.

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[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

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