Dynamics of the Formation of an Electron Bubble in Liquid Helium

The dynamics of excess electron localization in a bubble (equilibrium radius 17 Å) in liquid He is described in terms of the initial formation of an incipient bubble of radius 3.5Å, 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 $P=0\mathrm{}$ in liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ is ${\tau }_b=3.9\mathrm{}$ ps; the expansion time exhibits a marked pressure dependence (e.g., ${\tau }_b=1.5\mathrm{}$ ps at $P=16\mathrm{}$ 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.