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

抄録

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 D_2d symmetry (CO₂)₂^- in gas phase.