We perform the scanning tunneling spectroscopy based superconductor-vacuum-superconductor analogue to the seminal McMillan and Rowell superconductor-insulator-superconductor device study of phonons in the archetypal elemental superconductor Pb [W. L.
McMillan and J. M. Rowell, Phys. Rev. Lett. 14, 108 (1965)]. We invert this spectroscopic data utilizing strong-coupling Eliashberg theory to obtain a local {alpha}^2F({omega}) and find broad underlying agreement with the pioneering results, highlighted by previously unobserved electron-hole asymmetries and new fine structure which we discuss in terms of both conventional and unconventional superconducting bosonics.
