Tunneling in the case of an energy dependent density of states

We have solved a generalized set of three coupled Eliashberg gap equations which incorporate the effect of an energy-dependent electronic density of states N(epsilon). The model used for N(epsilon) was chosen on the basis of recent band structure calculations and the electron-phonon spectral density taken from tunneling results in Nb3Sn. The solutions are used to study of the effect of N(epsilon) on single particle tunneling into a superconductor. The theoretical characteristics so obtained are 'inverted' in the conventional way and the procedure is critically assessed. (orig.)