title: Normal mode spectra of two-dimensional classical atoms confined by a Coulomb potential.
abstract: The normal mode spectra of two-dimensional finite clusters of charged particles (-e) confined by a Coulomb potential resulting from a displaced positive charge Ze are obtained. This is a classical two-dimensional model system for atoms. We obtain the frequencies of the normal modes as a function of the confinement charge Z and the number of particles N. The analysis of the lowest normal mode frequency reveals a good agreement with the experimental results obtained in a system with screened interaction between charged particles. The dependence of the normal mode spectra as a function of a perpendicular magnetic field is also discussed and we found that the shear-like character of the modes is enhanced in the presence of the magnetic field. For large values of the magnetic fields the normal modes fall into two bands, a low frequency band with frequency approximately 1/omega(c) and a high frequency band with frequency approximately omega(c).
authors.affiliation: Departement Natuurkunde, Universiteit Antwerpen, Campus Drie Eiken, Universiteitsplein 1, B-2610 Antwerpen, Belgium. paiva@fisica.ufc.br
authors.forename: W P
authors.initials: WP
authors.lastname: Ferreira
authors.forename: F M
authors.initials: FM
authors.lastname: Peeters
authors.forename: G A
authors.initials: GA
authors.lastname: Farias