Long-lived metastable doubly positively charged diatomic ions of Mo-2(2+) have been produced by Ar+ bombardment of a molybdenum metal surface. These exotic molecular dications, such as for example Mo-92,95(2)2+ at m/z 93.5, could be observed in positive ion mass spectra for ion flight times of similar to17 mus in a Cameca IMS-3f secondary ion mass spectrometer, when the ion extraction field was adjusted for detection of ions that are formed in the gas phase several micrometers in front of the sputtered surface. MO22+ was observed at high primary current densities for projectile ions of Ar+, but could not be detected under very similar bombarding conditions for projectile ions of Xe+. Such a dependence of ion production by inert gas sputtering on the primary ion species [ionization energies: IP1(Ar)=15.76 eV and IP1(Xe)=12.13 eV] is unusual. It is shown that formation of Mo-2(2+) dications takes place by resonant charge transfer in grazing gas-phase collisions between incoming projectile ions of Ar+ and sputtered molecular ions of Mo-2(+). The efficiency for such a resonant electron capture (Mo-2(+) + Ar+ --> Mo-2(2+) + Ar) is of the order of 10(-5) for the bombarding conditions in our mass spectrometer and corresponds to a cross section of a few 10(-15) cm(2). (C) 2004 American Institute of Physics.