Excess-electron surface states of helium clusters

Bound states of an excess electron attached to the surface of helium clusters ⁴Heₙ and liquid helium are calculated. The binding energy increases smoothly from 0.04 cm^-1 for n=5×10⁵ to 5.57 cm^-1 for bulk liquid helium. The splittings of the first two excited states of the excess electron on a liquid-helium surface are reproduced to within 1% of the experimental values. We expect similar accuracies for the cluster states.