Rotons and Quantum Evaporation from Superfluid 4He

TL;DR

This paper uses density functional theory to calculate how rotons in superfluid helium cause quantum evaporation, predicting significant evaporation rates and analyzing reflectivity and reflection probabilities.

Contribution

It provides the first detailed quantum-mechanical calculation of roton-induced evaporation and reflection at superfluid helium surfaces, excluding phonon effects.

Findings

Sizable quantum evaporation rates from rotons.

Quantitative predictions for atomic reflectivity.

Analysis of roton change-mode reflection probabilities.

Abstract

The probability of evaporation induced by $R^+$ and $R^-$ rotons at the surface of superfluid helium is calculated using time dependent density functional theory. We consider excitation energies and incident angles such that phonons do not take part in the scattering process. We predict sizable evaporation rates, which originate entirely from quantum effects. Results for the atomic reflectivity and for the probability of the roton change-mode reflection are also presented.