Motion in a Bose condensate: VIII. The electron bubble

The Bose condensate model is used to elucidate the motion of the electron b ubble in superfluids. An asymptotic expansion is developed for steady subcr itical flow. Numerical integration of the coupled nonlinear Schrodinger equ ations, that describe the evolution of the wavefunctions of the Bose conden sate and the impurity, is used to study the nucleation and capture of vorte x rings. Because an electron bubble is made oblate by its motion relative t o the condensate, the critical velocity for the vortex nucleation is reduce d by about 20%, in agreement with experiments.