Electron mobilities mgr; in the low density gases are independent of electric field strength up to gsim;4 Td in benzene and gsim;5 Td in toluene. The ratio of the threshold drift velocity (for electron heating) to the speed of low frequency sound in the gas,vd(threshold)/co, is gsim;40 in benzene and gsim;50 in toluene. The ratios are gsim;3 fold higher than those in the saturated cyclic hydrocarbons cyclopentane and cyclohexane. The aromatic molecules have larger inelastic scattering cross sections than do the cycloalkanes for thermal energy electrons. The total scattering cross sections of benzene and toluene each have a minimum for electrons of sim;0.3 eV energy. The value of the total cross section averaged over a Maxwellian energy distribution at 300 K is 82 Aring;2for benzene and 87 Aring;2for toluene. A plot of mgr;nagainst densitynfor the coexistent vapor and liquid is horizontal atn1times;1020molecule/cm3in each vapor, slopes negatively to a minimum atnquest;1minus;2times;1021, increases to a maximum atnquest;3times;1021(n/nc=1.5), then plunges as the density is increased further. Electron quasilocalization occurs in the dense gas, and localization in the liquid. Quasilocalization is characterized by large negative values of Dgr;Hand Dgr;S, and a small value of Dgr;G, over a small temperature range near the vapor/liquid coexistence curve. The magnitudes of Dgr;Hand Dgr;Sand the extent of quasilocalization decrease as a constant density vapor is heated away from the coexistence region. A two state model of electron transport was applied to the results from the liquid phase.
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