Amplitudes And Level Spacings Of Bound-States In Superconducting Cd

Bound- and virtual-state structure has been observed in the tunneling characteristics of thick Cd films deposited over Pb. We observed amplitude effects displaying a temperature dependence not previously reported. An important point is made concerning basic spacings of bound and virtual levels. Amplitudes and level spacings appear to contain retrievable proximity-effect information. Taking nonlinear effects into account, a value of ${v}_{\mathrm{F}}=1.30\ifmmode\times\else\texttimes\fi{}{10}^{8}$ cm/sec is obtained for the $c$ direction.