Superconducting energy gap of BaPb1-xBixO3

We report the first infrared measurement of the superconducting energy gap of BaPb1-xBixO3. In our polycrystalline samples with Tc9.5 K (x0.2) we obtain 23.2kTc, roughly in agreement with the weak-coupling Bardeen-Cooper-Schrieffer prediction, 23.2kTc, and with tunneling measurements of the gap. We do not observe any structure above the gap energy associated with strong coupling. © 1988 The American Physical Society.