Time-resolved de photoconductivity has been used to observe quasifree electrons and solvent radical anions in supercritical CO2 (rho (c) approximate to 0.468 g/cm(3); T-c approximate to 31 degreesC). The electrons have lifetime tau (e) < 200 ps and mobility mu (e), > 10 cm(2)/(V s). For rho/rho (c) > 0.64, the product mu (e)tau (e) rapidly increases with the solvent density rho, reaching 2.5 x 10(-9) cm(2)/V at rho/rho (c) approximate to 1.82. The mobility of the solvent anions exponentially increases with p, being 2-10 times higher than the mobilities of other ions. The activation energy of the solvent anion migration is 0.46 eV, whereas for solute ions, this energy is less than 20 meV. Electron detachment upon 1.0-3.5 eV photoexcitation of the solvent anion has been observed. The cross section of photodetachment Linearly increases with photon energy above 1.76 eV end exhibits a shoulder at 2.82 eV; the spectrum is similar to photoelectron spectra of (CO2)(n)(-) clusters (n = 6-9) in the gas phase. Both the electrons and solvent anions react with nonpolar electron acceptor solutes whose gas-phase electron affinity (EA(g)) is greater than 0.4 eV. At T = 41 degreesC and rho/rho (c) approximate to 1.77, the rates of the electron attachment and solvent anion scavenging correlate with each other and the solute EA,. Only solutes with EA(g) > 2 eV exhibit diffusion-controlled kinetics. For pip, r 0.85, the scavenging radii of these diffusion-controlled reactions decrease with rho. For O-2, the scavenging of the solvent anion is reversible (DeltaH degrees approximate to -0.44 eV).