Abstract
We have studied the transition from second sound to ballistic phonon flow in He II up to pressures of 24 bar. At saturated vapor pressure the phonon-phonon scattering rate for K. At 24 bar, for K. The phonon-roton scattering rate is ∼ at 0.75 K and almost pressure independent. At 24 bar between 0.4 and 0.7 K, in addition to ballistic phonons, we observe a second pulse traveling at 16 m/sec, which we believe is the propagation of interacting rotons.
- Received 19 March 1973
DOI:https://doi.org/10.1103/PhysRevLett.30.1129
©1973 American Physical Society