Dynamics of the formation of an electron bubble in liquid helium.

Abstract

The dynamics of excess electron localization in a bubble (equilibrium radius 17 \AA{}) in liquid He is described in terms of the initial formation of an incipient bubble of radius 3.5\AA{}, followed by an adiabatic bubble expansion in the ground electronic state, which is described by a hydrodynamic model for the expansion of a spherical cavity in an incompressible liquid. The bubble expansion time at pressure $P=0$ in liquid $^{4}\mathrm{He}$ is ${\ensuremath{\tau}}_{b}=3.9$ ps; the expansion time exhibits a marked pressure dependence (e.g., ${\ensuremath{\tau}}_{b}=1.5$ ps at $P=16$ atm) and a small (3%) isotope effect in liquid $^{3}\mathrm{He}$. The interrogation of the electron bubble dynamics by femtosecond absorption spectroscopy is analyzed.