Quasiparticle current in ballistic NcS'S junctions

Nonstationary properties of ballistic constrictions $NcS^{\prime}S$ with disordered $S^{\prime}S$ electrodes are analyzed theoretically. Amplitudes of Andreev and normal reflections at the constriction are related to the solutions of a stationary Green function problem in an inhomogeneous $$ electrode in a dirty limit. This provides a generalization of the model of Blonder, Tinkham and Klapwijk for a spatially inhomogeneous case. The relation between quasiparticle current in $NcS^{\prime}S$ junctions and energy spectrum of a $S^{\prime}S$ proximity sandwich is found for arbitrary parameters of $S^{\prime}$ and $S$ materials and of $$ interface.