Nanoscopic jets and filaments of superfluid He-4 at zero temperature: a DFT study

TL;DR

This study uses density functional theory to explore how superfluid helium-4 jets and filaments break up or form vortex rings, revealing different behaviors based on jet length and filament aspect ratio.

Contribution

It provides a detailed DFT-based analysis of droplet formation and vortex nucleation in superfluid helium-4 jets and filaments, highlighting the effects of aspect ratio and jet dynamics.

Findings

Jet fragmentation follows linear inviscid fluid theory.

Filament contraction with high aspect ratio leads to vortex ring formation.

Vortex rings prevent filament breakup into droplets.

Abstract

Helium droplets produced by the instability of a cryogenic helium jet exiting a source chamber leads to the formation of He drops which are considered as ideal matrices for spectroscopic studies of embedded atoms and molecules. Here, we present a He-DFT description of droplet formation resulting from jet breaking and contraction of superfluid He-4 filaments. Whereas the fragmentation of long jets closely follows the predictions of linear theory for inviscid fluids, leading to droplet trains interspersed with smaller satellite droplets, the contraction of filaments with an aspect ratio larger than a threshold value leads to the nucleation of vortex rings which hinder their breakup into droplets.