高エネルギー電子ビームの超臨界流体中のラジカル・イオン反応への応用

概要

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A fast kinetic technique using high energy electron beams was applied to the study of reactions of radical ions in supercritical water and carbon dioxide. The high energy electron beams can easily ionize water molecules and produce hydrated electrons, OH radicals and H atoms. The reaction rate between the hydrated electrons and negative ions decreased with increasing temperature because of the repulsive interaction. On the other hand, the reaction rate between the hydrated electron and hydronium ions increased with temperature because of the attractive interaction. In supercritical CO2, dimer anions (CO2)2- and dimer cations (CO2)2+ were produced by ionization of CO2. Transient visible absorption spectra of these species were measured. Comparison with the photobleaching of CO2 anion clusters in solid rare gas matrices and their reactivity with H2 and O2 confirms the assignment. It is well established that the adiabatic electron affinity of CO2 is negative, but the adiabatic electron affinity of CO2 dimer has been calculated to be 0.89 eV for D2d symmetry (CO2)2- in gas phase.
2004-02-20