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

The instability of a cryogenic ⁴He jet exiting through a small nozzle into vacuum leads to the formation of ⁴He drops, which are considered ideal matrices for spectroscopic studies of embedded atoms and molecules. Here, we present a He-density functional theory (DFT) description of droplet formation resulting from jet breaking and contraction of superfluid ⁴He 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.