Electron collisions with diatomic anions
- Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)
- JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)
- Department of Physics, Atomic Physics, Stockholm University, S-10405 Stockholm (Sweden)
Electron collisions with negative ions (B{sub 2}{minus}, C{sub 2}{minus}, O{sub 2}{minus}, BN{sup {minus}}, and OH) have been performed in a merged- beams experiment at the heavy-ion storage ring ASTRID (Aarhus Storage Ring, Denmark). Absolute cross sections for detachment (e{sup {minus}}+AB{sup {minus}}{r_arrow}AB{sup 0}+2e{sup {minus}}) and detachment plus dissociation (e{sup {minus}}+AB{sup {minus}}{r_arrow}A{sup 0}+B{sup 0}+2e{sup {minus}}) are reported for energies below 40 eV. For the homonuclear ions, X{sub 2}{sup {minus}} (X=B,&hthinsp;C,&hthinsp;O), cross sections are also presented for dissociative reactions leading to an X{sup {minus}} particle in the final state. The detachment process is dominant for all investigated systems. The detachment cross section is characterized by an effective threshold larger than the electron binding energy. The shapes of the detachment cross sections are similar for the studied anions pointing to a common nonresonant mechanism for detachment. Also, the cross section for detachment plus dissociation and pure dissociation show regularities pointing to a general nonresonant mechanism. Structures are observed in the detachment cross section of C{sub 2}{sup {minus}} and BN{sup {minus}} and in the dissociation cross section of B{sub 2}{minus} and C{sub 2}{minus}. The structures are attributed to short-lived dianions (resonances) formed during the collision process. The results are supported by {ital ab initio} calculations, and it is inferred that electronic excitations are important in the resonant reactions. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 692506
- Journal Information:
- Physical Review A, Vol. 60, Issue 4; Other Information: PBD: Oct 1999
- Country of Publication:
- United States
- Language:
- English
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