Rydberg states of alkali atoms on superfluid helium nanodroplets: inside or outside?Electronic supplementary information (ESI) available: Several figures detailing the results of this work. The accuracy of the Chebyshev method is addressed and additional figures are presented for other alkali metal atoms besides Rb. See DOI: 10.1039/c7cp02332d

Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid 4 He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential. The application of a spectral method to the radial part of the valence electron wavefunction allows the computation of highly excited Rydberg states. For low principal quantum numbers, the energy required to push the electron outward is larger than the solvation energy of the ion. However, for higher principal quantum numbers the situation is reversed, which suggests the stability of a system where the ion sits inside the droplet while the valence electron orbits the nanodroplet. Electronic excitations of an electron bound to an alkali metal ion inside a droplet of superfluid 4 He are computed via a combination of helium density functional theory and the numerical integration of the Schrödinger equation for a single electron in a modified, He density dependent atomic pseudopotential.