Interaction of Helium Rydberg State Atoms with Superfluid Helium

Abstract

The pair potentials between ground state helium and Rydberg He ∗ (2s, 2 p, 3s) atoms are calculated by the full configuration interaction electronic structure method for both the electronic singlet and the triplet manifolds. The obtained pair potentials are validated against existing experimental molecular and atomic data. Most states show remarkable energy barriers at long distances (R > 5 A), which can effectively stabilize He ∗ against the formation of He ∗ at low nuclear kinetic energies. Bosonic density functional theory calculations, based on the calculated pair potential data, indicate that the triplet ground state He ∗ reside in spherical bubbles in superfluid helium with a barycenter radius of 6.1 A at the liquid saturated vapor pressure. The pressure dependency of the relative He ∗ 2s 3 S → 2 p 3 P absorption line blue shift in the liquid was obtained through both the statistical line broadening theory as well as the dynamic adiabatic following method. The pronounced difference between the results from the static and dynamic models is attributed to the dynamic Jahn-Teller effect that takes places in the electronically excited state within the dephasing time of 150 fs. Transient non-thermalized liquid surroundings near He ∗ may contribute to an artificial reduction in the absorption line blue shift by up to 30 cm −1 .