Electron scattering on CN-

We present the results of an experiment in which electrons have been scatte red on CN- ions, over a collision energy range 0-60 eV The experiment was p erformed at the heavy ion storage ring CRYRING The CN- ions were stored in the ring and merged with a monoenergetic electron beam that was guided in t o and out of the ring using strong magnetic fields. Both neutral and positi ve fragments from the collision process were detected with surface barrier detectors. It was found that pure detachment completely dominates over thos e channels which involves breaking the molecular bond. The threshold energy for the detachment process was found to be 7 eV The cross section rose fro m zero to a maximum of about 5.10(-16) cm(2) just below 30 eV, after which it remained essentially constant. The threshold region was carefully invest igated in an attempt to find resonance structure arising from the possible existence of the doubly charged ion, CN2-. The statistical uncertainty in t he data was, however, too large to conclusively prove or disprove the exist ence of such a resonance.