The Creation of Long-Lived Multielectron Bubbles in Superfluid Helium

Abstract

Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes. MEBs in liquid helium are predicted to have dynamic instabilities for zero or positive pressures, and stability for negative pressures. We report the production of long-lived MEBs in a novel cell filled with helium at static negative pressures. MEBs were extracted from the vapor sheath of a heated filament loop embedded in the superfluid helium and were observed by high-speed photography as they rose in the helium under buoyant forces. In earlier studies we found that MEBs created in this way had large amplitude oscillations and were unstable to decay. By creating MEBs at temperatures just under the lambda point, these oscillations are rapidly damped and the MEBs relax toward a spherical shape and stability as they rise in the helium.