Time-domain analysis of electronic spectra in superfluid 4He

Electronic absorption spectra of impurities in superfluid helium is developed in time domain, using time-dependent density functional theory to describe liquid 4He and time-dependent perturbation theory to describe the electronic degrees of freedom of the impurity. Angularly isotropic potentials are used to describe the molecule–helium interactions in the ground and excited electronic states. The calculations rationalize experimentally observed phonon side-bands in 4He droplets and in bulk helium, and allow assignments of spectral features to specific motions of the liquid.