When an electron enters liquid helium, it experiences a repulsive potential V0 of approximately 1 eV [1]. As a consequence it is energetically favorable for the electron to become localized within a spherical volume from which the helium is nearly completely excluded [2]. As a first approximation one can consider that the energy E is the sum of the zero-point energy of the electron, the surface energy of the bubble, and a volume energy proportional to the applied pressure P, i.e.,