Ab-initio relativistic density functional calculations for spectral line shifts of Rb atoms in liquid helium

Accurate laser spectroscopic studies of the principal resonance transitions in Rb and Cs atoms embedded in liquid helium have shown appreciable line shifts and change in line profiles. A pilot attempt has been made here to compute ab-initio the spectral line shift of the resonance excitation lines in Rb under such a confinement. Relativistic density functional theory (RDFT) within local density approximation (LDA) has been adopted. A model cluster of fourteen helium atoms surrounding the central Rb is assumed. With an optimized radius of the cluster of 5.15 A the RLDA estimate of the blue shift of the lowest 2S → 2P excitation line of Rb comes out to be 15.4 nm which compares very well with the experimental value of 16.4 nm