Electron Attachment to CO₂ in Supercritical Ethane

Masaru Nishikawa, Kengo Itoh and Richard A. Holroyd

J. Phys. Chem. A 103, 550-556 (1999) [Find paper at ACS Publications]

Abstract:

Thermal electrons attach reversibly to CO₂ in supercritical ethane. The equilibrium constants range from 40 to 2 x 10⁴ molal^-1 for pressures from 50 to 220 bar at 33 and 37 C. The attachment rate increases and the detachment rate decreases as the pressure increases. The lifetime of CO₂^- is between 20 and 100 ns in the high pressure range. The reaction volume changes more than an order of magnitude, from -20.0 to -0.5 l/mol, over the pressure and temperature ranges studied. The activation volume is approximately 50% of the reaction volume. Electrostriction volumes of CO₂^- ion, calculated by a compressible continuum model, account for the main part of the observed reaction volumes. The calculation shows that the high density region around each CO₂^- extends to 1 nm.