VERTEX-CORRECTED TUNNELING INVERSION IN SUPERCONDUCTORS

We have generalized the McMillan-Rowell tunneling-inversion program, w hich extracts the electron-phonon spectral function alpha(2)F(Omega) a nd the Coulomb pseudopotential mu from experimental tunneling data, t o include the lowest-order effect of vertex corrections. In so doing, the momentum dependence of the electron-phonon matrix elements are neg lected, which is equivalent to using a local approximation. The vertex -corrected strong-coupling perturbation theory is performed on the ima ginary axis and then an exact analytic continuation is used to produce the density of states on the real axis. Comparison with the experimen tal data for Pb indicates that effects of vertex corrections may be ob servable even in low-temperature superconductors.