Evaluation of spectral line width of atoms in liquid helium

A CASPT2 study of the spectral shift of the resonance emission lines of Rb and Cs embedded in liquid He

“…Due to dominating van der Waals interaction between He and the central atom only nearest neighbors are mostly effective in producing the shift. Hence, the basic advantage here is the relatively small number of He atoms surrounding the central foreign atom to represent the cluster and its symmetry ensuring efficient calculation [16,23,24]. This model ignores the structural fluctuation of the liquid He atoms around the mean position and hence the width of the spectral lines cannot be calculated [16].…”