title: Unusual Rydberg system consisting of a positively charged helium nanodroplet with an orbiting electron.
abstract: Evidence is presented of an unusual Rydberg system consisting of a helium nanodroplet containing a positively charged sodium ion and an orbiting electron. Rydberg states of this system with principal quantum number n<20 are found to be unstable on a nanosecond time scale. In contrast, Rydberg states with n≳100 are found to have a lifetime of 1.1 μs. In addition, it is found that the ionization threshold of sodium-doped helium is broadened and redshifted with respect to that of the free atom. These observations are successfully reproduced using a pseudodiatomic description of the system in which the interactions of the sodium and its ion with the helium are calculated as the sum of pair potentials.
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: Evgeniy
authors.initials: E
authors.lastname: Loginov
authors.forename: Marcel
authors.initials: M
authors.lastname: Drabbels