Double ionization of van der Waals dimers: NeXe and ArXe

Abstract

Simple consideration of atomic first and second ionization potentials show that for certain atomic combinations stable diatomic ions carrying two positive charges should exist below the lowest dissociation limit. One such ion NeXe++ has been observed experimentally by double ionization of the van der Waals dimer NeXe. Similar experiments also resulted in production of a long-lived ArXe++ ion. The stability of these doubly charged molecular ions is rationalized using semiquantitative potential curves derived from the isoelectronic neutral molecules XeO and ICl. The appearance potentials found experimentally for both doubly charged molecular ions are consistent with the predictions from the potential energy curves. Some observations of other investigators on the kinetics of the low lying states of Xe++ in Ar and Ne are reinterpreted.