CONICET | Buscador de Institutos y Recursos Humanos

Five homonuclear diatomic dications Zr22+, Cd22+, Hf22+, W22+, and Pt22+ have been observed in the gas phase by mass spectrometry. These exotic doubly positively charged molecules were producedindirectly in the ion extraction region of a secondary ion mass spectrometer during sputtering of zirconium, cadmium, hafnium, tungsten, and platinum metal foils, respectively, by energetichigh-current Ar+ ion surface bombardment. They were detected in positive ion mass spectra at half-integer m/ z values for ion flight times of the order of 10−5 s. To our knowledge, these specieshad not been observed before. This experimental work confirms two theoretical investigations that had predicted that W22+ and Cd22+ are long-lived metastable species in the gas phase, but contradictstwo theoretical studies that had suggested that Pt22+ should be unstable with respect to fragmentation. Therefore an advanced theoretical investigation of the ground state of Pt22+ was alsoperformed. Our calculation shows that the ground state of Pt22+ is metastable with an internuclear equilibrium distance of 2.36 Å, a dissociation energy with respect to the top of the barrier of2.32 eV, and an ionization potential of Pt2+ of about 15.8 eV. The latter theoretical result strongly suggests that Pt22+ dication formation in our experiment may have taken place via the resonant electron transfer process Pt2+ + Ar+ → Pt22+ + Ar.