Nature of exotic negative carriers in superfluidHe4

Abstract
The mysterious ‘‘fast’’ and ‘‘exotic’’ negative carriers in liquid He4 are interpreted as multielectron bubbles. The fast carrier is shown, by a detailed calculation of mobility, to be a two-electron bubble with a radius of approximately 30 Å. A crucial role is played by the unusual kinematics of rotons, which have not previously been adequately treated. The other exotic carriers are multielectron bubbles with higher charges.