Spectroscopy of single atoms in the scanning tunneling microscope

A study is presented of the bias dependence of the tunneling current between two planar metal electrodes, each of which has an adsorbed atom. (One atom can be thought of as the tip, the other as the sample.) The positions of the peaks in a plot of the calculated $\frac{d\ln I}{d\ln V}$ versus $V$ show a close correspondence to the positions of the resonances in the densities of states of both sample and tip.