Stability of multi-electron bubbles in liquid helium
  The stability of multi-electron bubbles in liquid helium is investigated theoretically. We find that multi-electron bubbles are unstable against fission whenever the pressure is positive. It is shown that for moving bubbles the Bernoulli effect can result in a range of pressures over which the bubbles are stable. 
Wei Guo, Dafei Jin, and Humphrey J. Maris