Second-sound attenuation very near $T_{\lambda }$ is found to be proportional to the square of the frequency, and the damping diverges as ${(T_{\lambda }-T)}^{-\sigma }$, $\sigma =0.34\mathrm{}\pm 0.06$, in agreement with dynamic scaling. The coefficient of the damping is consistent with recent estimates of the coherence length.

• Received 5 August 1968

DOI:https://doi.org/10.1103/PhysRevLett.21.1235