Electronic Properties of Negative Ions in Liquid Helium

The electronic properties of a negative ion in liquid ${\mathrm{He}}^4$ are investigated theoretically. It is assumed that the ion consists of an electron trapped in a bubble, represented by a square-well potential of depth ∼ 1 eV. Explicit analytic formulae are obtained which are useful for computing many properties of such an electron, including direct optical absorption and scattering of light accompanied by $1s-ns$ and $1s-nd$ transitions. Numerical values are given for the strength of $1s-1p$ transitions and for the scattering cross sections of laser light due to $1s-2s$ and $1s-1d$ transitions. The splitting of the $1p$ state due to the Jahn-Teller effect is investigated in detail, and the linewidths for the scattering processes are estimated.