Negative ions in CO2

• Published in: The Journal of chemical physics 1977-04, Vol.66 (7), p.3246-3251
• Main Authors: Fansler, T. D., Colonna-Romano, L. M., Varney, R. N.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.434300

Reaction rate coefficients for negative ions in CO2 according to the reaction O−+2CO2⇄kCBkBCCO3 − +CO2 have been evaluated experimentally over a range of 45⩽E/N⩽400 Td at 320±2 °K. Most of the measurements were made with a drift-tube mass spectrometer operated in a mode to gate electrons as well as negative ions. The attachment of electrons in the drift tube introduces details into the arrival time spectra of the ions that enhance the resolving power for evaluation of rate coefficients. At low E/N, kBC approaches (5±0.5) ×10−28 cm6 s−1, and declines slowly with increasing E/N. The value of kCB is negligible below E/N=300 Td, then rises steeply to ≃1×10−11 cm3 s−1 at 400 Td. Changes of gas temperature have been shown to act to shift the reaction equilibrium in the same sense that changes in E/N do. At E/N⩾200 Td, collisional detachment of electrons from O− occurs according to the reaction O−+CO2kBA→e−+CO2+O and the rate rises steeply with E/N. At 400 Td, kBA reaches 9×10−12 cm3 s−1.