Relative Evaporation Probabilities of 3He and 4He from the Surface of Superfluid 4He

TL;DR

This study investigates the evaporation of 3He and 4He atoms from superfluid 4He, revealing that high-energy phonons can evaporate both isotopes with similar likelihood, while rotons predominantly evaporate 4He.

Contribution

It demonstrates that high-energy phonons can evaporate 3He atoms in superfluid 4He with similar probability to 4He, and establishes a low probability of rotons evaporating 3He.

Findings

High-energy phonons evaporate 3He and 4He with equal probability.

Rotons are unlikely to evaporate 3He, with probability less than 2% of evaporating 4He.

3He atoms in Andreev states are evaporated by high-energy phonons.

Abstract

We report a preliminary experiment which demonstrates that 3He atoms in Andreev states are evaporated by high-energy (E/k_B ~ 10.2 K) phonons in a quantum evaporation process similar to that which occurs in pure 4He. Under conditions of low 3He coverage, high-energy phonons appear to evaporate 3He and 4He atoms with equal probability. However, we have not managed to detect any 3He atoms that have been evaporated by rotons, and conclude that the probability of a roton evaporating a 3He atom is less than 2% of the probability that it evaporates a 4He atom.