On the stability of the singly and doubly charged beryllium trimers Be+3and Be++3

Abstract

Extensive multireference configuration interaction calculations were carried out to generate adiabatic potential energy surfaces for the electronic ground state of Be+ 3 and Be++ 3. Resulting stability and other properties are investigated, showing that Be+ 3 is stable in a linear symmetric equilibrium configuration with a bond length R e = 2·28 Å and dissociation energy D e = 1·16 eV, the associated electronic state being 2Σ+ g. The doubly charged system Be++ 3 is found to be metastable due to relatively large and wide energy barriers. The corresponding local energy minimum occurs also in a linear symmetric geometry with R e = 2·17 Å, but is unbound by 1·44eV. A WKB estimate for the tunnelling dissociation shows that the lifetime of Be++ 3 is sufficiently long to allow its experimental observation.