Long lived CH2+ and CD2+ dications

A search for long lived CH2+ and CD2+ dications formed in fast charge strip ping collisions of CH+ and CD+ on Ar was conducted. An experimental method based on the detection of the H (or D) fragments of the dication was develo ped, in order to eliminate possible confusion with C-13(2+) for the first a nd N-14(2+) for the latter. The flight time of these dications through the apparatus is about 70 ns, well below the 3 mu s time associated with earlie r observations of CH2+. Our measurements indicate that no long lived states of either of these dications are formed in fast charge stripping collision s. However, this result does not exclude the possibility that long lived st ates, like the excited A (2)Sigma(+) metastable state, are populated in slo w charge stripping collisions. (C) 1999 Elsevier Science B.V.