Calculation of the Cross-Section for Optical Transitions of an Electron Bubble to D States

The optical transitions of an electron bubble (negative ion) in liquid helium from the ground state to the 1P and 2P states have been studied in a number of experiments. For an ideal spherical bubble electric-dipole transitions can occur only to P states. Thermal or quantum fluctuations in the bubble shape make other transitions possible. In this paper we calculate the cross-sections for transitions from the 1S ground state to the 1D and 2D states. The cross-section for the 1S to 1D transition is approximately two orders of magnitude less than the cross-section for the 1S to 1P.