Microwave Properties of Superconducting Zinc in the Energy-Gap Frequency Region

Microwave measurements of the relative power absorbed at resonance have been made with a pure, polycrystalline zinc cavity. The data taken in a He³ cryostat covered the frequency range from 50 to 75 kMc/sec and the temperature range from above the superconduting transition, Tc=0.825±0.008^∘K, down to 0.28^∘{}K. The results extrapolated to 0^∘{}K yield an energy gap of (3.01±0.09) kTc. The detailed comparison of RₛRₙ versus frequency showed good agreement in the Pippard limit with the BCS calculations scaled to the experimentally determined gap. A plot of RₛRₙ versus hνEg(0) for zinc and aluminum showed that the law of corresponding states was valid to about 5%.