Reactivity of charged species and cluster in supercritical fluids -Fast time-resolved spectroscopy and conductivity study-

超临界流体最显著的特征是在临界点附近压缩性的发散性增加，这是带电物质行为的控制因素。超临界Xe和Kr中的多余电子是准自由的，它们在各自的临界密度以下的迁移率可以用形变势理论根据声学声子散射利用绝热压缩性来精确预测2。准分子（Xe_2^*）是由Xe_2^+与电子复合而产生的。Xe_2^*可被乙烷等分子添加剂迅速淬火。在接近临界点时，电子附着在溶质上的反应速率急剧增加，这是由于簇形成所产生的离子的稳定。与C_6F_6的吸附速率常数达到1×10^<15>m^<-1>s^<-1>，而与氧的吸附速率常数仅为2×10^<11> m^<-1>s^<-1>。前一反应的活化体积可用连续介质可压缩模型来描述。从C_6F_6^-离子到苯醌的电荷转移反应是扩散控制的，在等温压缩峰值密度处达到最大值1.8×10^<11> m^<-1>s^<-1>。

The most salient feature of supercritical fluids is the divergent increase of compressibility near the critical point, which is the governing factor of the behavior of charged species.1. Excess electrons in supercritical Xe and Kr are quasi-free and their mobility below the respective critical density can be accurately predicted by the deformation potential theory in terms of acoustical phonon scattering utilizing adiabatic compressibility2. The excimer (Xe_2^*) is produced by the recombination of Xe_2^+ with electrons. Xe_2^* can be quenched rapidly by molecular additives like ethane.3. Reaction rates of electron attachment to solutes increase sharply near the critical point due to stabilization of resultant ions by cluster formation. The rate constant for attachment to C_6F_6 reaches 1×10^<15>m^<-1>s^<-1>, however, that with oxygen is only about 2×10^<11> m^<-1>s^<-1>. The activation volume for the former reaction can be described by the continuum compressible model.4. Charge transfer reaction from C_6F_6^- ion to benzoquinone is diffusion-controlled and reaches a maximum 1.8×10^<11> m^<-1>s^<-1> at the density of isothermal compressibility peak.