We have calculated the ratio of the energy gap Ao to the critical temperature T, for a large number of known electron-phonon spectral densities with the use of the imaginary-axis formulation of Eliashberg theory with an analytic-continuation technique to the real axis. Agreement with experiment is within a few percent. It is found that the general trend obtained for 2AO/kqT, against T, /coh, where co&" is the popular Allen-Dynes expression for the average phonon energy, can be reproduced by a two-parameter functional form of the general type first given by Geilikman andKresin. The details, however, can only be understood with complete calculations.

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We have studied the effects that the existence of spin fluctuations on the normal side of a proximity sandwich can have on superconducting properties. We consider the critical temperature, its functional derivative with paramagnon spectral density, the frequency-dependent gap, and the quasiparticle density of states. The question of the interplay of phonon and paramagnon structure in tunneling characteristics is addressed. Comparison with experiment is made for the case of Pd.

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