Excess electron surface states on helium clusters

M. Rosenblit*, Joshua Jortner

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


In this paper we report on quantum mechanical calculations for the ground and the excited electronic surface states of an excess electron on (He) N clusters (N=3.5×105-6×1023), exploring the cluster size dependence of the excess electron localization and the bridging between the properties of the electron on cluster microsurfaces and on flat macrosurfaces. Representing the e-(He)N potential by a short-range repulsive model potential or by a pseudopotential, together with a long-range attractive dielectric image potential, we have shown that the electronic energies are relatively insensitive (i.e., within 20% for N=10 6 and within 6% for N≥107) to the details of the short-range repulsive interactions. The model potential results in a "critical" radius Rc(1,0)=148 Å with a number of constituents Nc(1,0)=3.0×105 for electron localization in the ground n=1, l=0 electronic state, while with a further increase of the cluster radius R above Rc(1,0), higher n,l states become localized at cluster radii Rc (n,l), with Rc(n,l′) > R c(n,l) for l′>1 and Rc (n′,l′) > Rc(n,l) for n′>n and for all values of l and l′. The energies En,l of the n,l electronic states above the localization threshold are characterized by the scaling relations En,l(R)∝(R-R c(n,l))η(l) with η(l)=2 for l=0 and η(l)=1 for l≠0. The-charge distribution in this size domain for l=0 is characterized by the moments 〈rJ〉∝(R-R c(n,0))-J, while for l=1, 〈r〉∝ (R-Rc(n,1))-1/2. The "critical" cluster radii for localization obey algebraic relations, which result in the cluster size dependence of the number of bound electronic states. Cluster surface size equations were obtained for R→∞ providing a quantitative description of the convergence of the electronic energies to those for a flat surface. Information on electronic spectroscopy was inferred from the cluster size dependence of the transition energies and oscillator strengths for the 1,0(1s)→n,1(np) electronic excitations. The 1s→1p electronic transition is characterized by a transition energy and an oscillator strength which both decrease as R-2, manifesting the onset of l degeneracy for macrosurfaces. Finally, electric field effects provide information on field-induced ionization and huge polarizabilities αc≃ (109-1011H (where αH is the polarizability of the hydrogen atom) of these giant excess electron states.

Original languageEnglish
Pages (from-to)9982-9996
Number of pages15
JournalThe Journal of Chemical Physics
Issue number11
StatePublished - 1994


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