Electron mobility table hydrocarbons

Table 3 Electron Mobilities in Hydrocarbons and Their Derivatives...

Electron mobility is an activated process in low-mobility hydrocarbon liquids. The mobility in these liquids increases with temperature with activation energy exceeding 0.1 eV In a few high-mobility liquids, the measured activation energy lies between -0 to 0.05 eV (see Table 10.1) in many others, the mobility decreases with temperature. Intermediate mobility liquids show complex behavior, although some of these have activation energies 0.1 to -0.05 eV. 

Table 10.4 lists the values of trap density and binding energy obtained in the quasi-ballistic model for different hydrocarbon liquids by matching the calculated mobility with experimental determination at one temperature. The experimental data have been taken from Allen (1976) and Tabata et ah, (1991). In all cases, the computed activation energy slightly exceeds the experimental value, and typically for n-hexane, 0/Eac = 0.89. Some other details of calculation will be found in Mozumder (1995a). It is noteworthy that in low-mobility liquids ballistic motion predominates. Its effect on the mobility in n-hexane is 1.74 times greater than that of diffusive trap-controlled motion. As yet, there has been no calculation of the field dependence of electron mobility in the quasi-ballistic model. 

From the intercept at E = 0 of the linear portion of the photocurrent, the quantum yield of free ions is obtained. The zero field quantum yield is a function of the photon energy and of the nature of the solvent. In Figure 7, the spectral dependence of the quantum yield for photoionization of TMPD in three solvents is shown. Roughly, a correlation exists between the quantum yield and the electron mobility of each solvent. In tetramethylsilane = 100 crrPV s ) higher quantum yields are measured as compared to n-hexane (Pei = 0.1 cm2V" s" ). Aromatic molecules were studied in a variety of hydrocarbon solvents (Choi et al., 1982 Holroyd et al. 1983, 1984). Some results for the photoionization energy are summarized in Table 4. 

As it has been already indicated in Sect. 2, electron transport through the hydrocarbon core of the bilayer (see reactions (8), (14), (26)) is a key step of any transmembrane PET, and usually it controls the rate and efficiency of the PET process as a whole. Therefore, the data concerning the mechanism of this stage of PET and the factors which affect it are of crucial importance for the development of photochemical systems based on PET across the membranes. Unfortunately, for the majority of the systems listed in Table 1 the proposed mechanisms of electron transfer across the membrane seem to be rather tentative because of insufficient information about the localization of the redox-active components and their diffusion mobility inside the membranes. Only for few systems the studies were detailed enough to propose convincing mechanisms and to give a quantitative description of the kinetics of electron transfer across the membrane. 

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