“Quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen

We report the first observation of “quasi-Planck” spectra of capillary turbulence on the surface of liquid hydrogen in the dissipation domain. Capillary waves have been driven by low-frequency random force. We have observed that the frequency spectrum of surface elevation changes its dependence from power-like $\langle|\eta_\omega^2|\rangle\sim\omega^{-2.8}$ at middle-frequency domain to “quasi-Planck” distribution $\sim e^{-\omega/\omega_d}$ at higher frequencies. The frequency $\omega_d$ is proportional to the boundary frequency between inertial interval and dissipation domain and it is scaled up with the increase of driving force.