Collision-induced electron detachment and dissociation of carbon cluster dianions: (C₇)^2-and (C₁₀)^2-

Carbon cluster dianions (C-7)(2-) and (C-10)(2-) were produced by sputtering of a graphite sample and detected by accelerator mass spectrometry (AMS). The collisional activation of these dianions was studied via their interaction with He gas in an ion beam cooler device which is part of the AMS instrument. Contrary to the respective monoanion cluster, the stability of the dianions exhibits a very pronounced dependence on the gas pressure (i.e., the He gas density). Above a specific value, the transmitted intensity of both dianions decreases strongly pointing to the occurrence of collision-induced reactions. From the observed reaction products, it is concluded that both electron detachment and dissociation take place upon collisions with the gas atoms, following generic pathways such as (C-n)(2-) -> (C-n)- + e(-) and (C-n)(2-) -> (Cn-m)(-) + (C-m)(-).