Electron-impact detachment and dissociation of C4- ions

CRYRING was used to study collision processes between an electron and a negative ion cluster C-4(-). The total detachment cross sections for the production of the neutral 4C, 3C, 2C, and C fragments were measured. The cross sections for pure detachment, and for detachment plus dissociation leading to the production of C-3+C, 2C(2), and C-2+2C were extracted using a grid. It was found that the pure detachment process overwhelmingly dominates all other fragmentation processes. The threshold location for the detachment channel is found to be around 6.0 eV. Although the doubly charged negative ion C-4(2-) has received little previous attention, a defined near-threshold resonance observed in the detachment cross section curve, has been associated with the short-lived state C-4(2-) (0.7 fs lifetime). (C) 2001 American Institute of Physics.