Parametric excitation of second sound by first sound in liquid helium II
Pushkina N.I., Khokhlov R.V.
We consider nonlinear combination (Raman) interaction of first sound with second sound in liquid helium II—parametric excitation of second sound by an exciting first-sound wave. An expression is obtained for the threshold intensity of the first sound, at which excitation the second-sound waves set in. The possibility of experimentally observing the phenomenon is discussed.