Femtosecond room-temperature measurement of the electron-phonon coupling constant γ in metallic superconductors

We report the first systematic femtosecond pump-probe measurements of the electron-phonon coupling constant λ in thin films of Cu, Au, Cr, Ti, W, Nb, V, Pb, NbN, and ${\mathrm{V}}_3$Ga. The agreement between our measured λ values and those obtained by other techniques is excellent, thus confirming recent theoretical predictions of Allen. By depositing thin Cu overlayers when necessary, we can extend this technique to nearly any metallic thin film.