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On the basis of experimental evidence that the effective superconducting penetration depth is increased by a decrease in electronic mean free path, whether by body or surface scattering, and guided by the Pippard nonlocal theory, we propose that many types of experiments on small particles can be interpreted semi-quantitatively by taking over the formal results of the London theory with ₀ modified to ₀ (1+{{₀}{l₄₅₅}) }^1{2}. In this, ₀ is Pippard's coherence length and 1{l₄₅₅} includes both surface and body scattering. This method gives a good fit to Whitehead's susceptibility data on colloidal superconducting mercury, but predicts a narrower nuclear resonance line than is observed by Reif in a similar colloid.
M. Tinkham (Tue,) studied this question.