Nondissociative low-energy electron attachment to c-C7F14 and C6F6: Intermediate lifetimes

Nondissociative electron attachment to c-C7F14 and C6F6 is investigated by measuring the velocity distribution of K+ ions formed via electron transfer in collisions with velocity selected K(np) Rydberg atoms and by measuring the decay of the product negative ions during passage to a detector. Collis ions with C7F14 lead to the production of free electrons and of long-lived (tau > 100 mu s) C7F14-* ions. The free electrons, which result from autode tachment, are all created within a very short time period (tau less than or similar to 15 ps) following initial electron capture. Collisions with C6F6 result in the formation of C6F6-* ions that have a broad range of lifetime s against autodetachment. A possible reaction model involving competition b etween autodetachment and intramolecular vibrational relaxation is discusse d. (C) 1999 American Institute of Physics. [S0021-9606(99)02440-X].