Electron drift

Assuming that the current in the gas is carried mostly by electrons, the induced electric field uB causes transverse electron motion (electron drift), which, being itself orthogonal to the magnetic field, induces an axial electric field, known as the Hall field, and an axial body force, F, given by... 

Fig. 2. Electron drift velocities as a function of electric field for A, GaAs and B, Si The gradual saturation of curve B is characteristic of all indirect semiconductors. Curve A is characteristic of direct gap semiconductors and at low electric fields this curve has a steeper slope which reflects the larger electron mobiUty. The peak in curve A is the point at which a substantial fraction of the electrons have gained sufficient energy to populate the indirect L minimum which has a much larger electron-effective mass than the F minimum. Above 30 kV/cm (not shown) the drift velocity in Si exceeds that in...

In the naphthyridine ring with its 10 delocalized 7r-electrons located on five distorted molecular orbitals, due to an electron drift toward the nitro-... 

Figure 10.1a shows electron drift velocity as a function of electric field in methane, NP, and TMS (sublinear cases) according to the data of Schmidt and co-workers. These are contrasted in Figure 10.1b with supralinear drift velocity in neohexane, ethane, 2,2,2,4-TMP, and butane at the indicated temperatures In the case of neohexane, the drift velocity has been found to be proportional to the field up to 140 KV/cm (Bakale and Schmidt, 1973b). 

In certain liquids, the electron drift velocity shows peculiar behavior under special circumstances, some of which will now be described. 

In 1925, Robinson first published his schematic "curly arrows," indicating electron drift or displacement, 124, defining nitrosobenzene as a crotenoid reactant. 

Classical Free-Electron Theory, Classical free-electron theory assumes the valence electrons to be virtually free everywhere in the metal. The periodic lattice field of the positively charged ions is evened out into a uniform potential inside the metal. The major assumptions of this model are that (1) an electron can pass from one atom to another, and (2) in the absence of an electric field, electrons move randomly in all directions and their movements obey the laws of classical mechanics and the kinetic theory of gases. In an electric field, electrons drift toward the positive direction of the field, producing an electric current in the metal. The two main successes of classical free-electron theory are that (1) it provides an explanation of the high electronic and thermal conductivities of metals in terms of the ease with which the free electrons could move, and (2) it provides an explanation of the Wiedemann-Franz law, which states that at a given temperature T, the ratio of the electrical (cr) to the thermal (k) conductivities should be the same for all metals, in near agreement with experiment ... 

For many nonpolar liquids, the electron drift mobility is less than 10 cm /Vs, too low to be accounted for in terms of a scattering mechanism. In these liquids, electrons are trapped as discussed in Sec. 4. Considerable evidence now supports the idea of a two-state model in which equilibrium exists between the trapped and quasi-free states ... 

A survey is given of the theoretical and experimental studies of electron-ion recombination in condensed matter as classified into geminate and bulk recombination processes. Because the recombination processes are closely related with the magnitudes of the electron drift mobility, which is largely dependent on molecular media of condensed matter, each recombination process is discussed by further classifying it to the recombination in low- and high-mobility media. 

Electroded TOF experiments have already been described previously [29]. They were carried out under small-signal conditions to determine hole and electron drift mobility. Carriers were generated by illuminating the sample through the... 

Figure 5.9 Hole and electron drift mobility lifetime product /xt and residual potential versus Te content in a-Scj- Te films. The /xt product was xerographically measured by Abkowitz and Markovics [14].

The effect of Sb on electron transport is not so drastic. Although Sb alloying increases the transit time dispersion, the transit time shown contains a clearly identifi-ably break in the waveform. The electron drift mobihty in a-Sb Sci alloys exhibits Arrhenius behavior. The experimentally observed activation energy of a-Se—namely,... 

The peculiar metal ion specificity of the ATP cleavage reaction may perhaps be explained by reference to some studies on the metal complexes of Schiff bases, which have provided clues to many aspects of biological metal catalysis. It was shown that metal ions will split the carbon-nitrogen double bond in thiophenalde-hyde-ethylenediamine (18, 21) as a consequence of the electronic-drift-to-metal... 

Up to now, only hydrodynamic repulsion effects (Chap. 8, Sect. 2.5) have caused the diffusion coefficient to be position-dependent. Of course, the diffusion coefficient is dependent on viscosity and temperature [Stokes—Einstein relationship, eqn. (38)] but viscosity and temperature are constant during the duration of most experiments. There have been several studies which have shown that the drift mobility of solvated electrons in alkanes is not constant. On the contrary, as the electric field increases, the solvated electron drift velocity either increases super-linearly (for cases where the mobility is small, < 10 4 m2 V-1 s-1) or sub-linearly (for cases where the mobility is larger than 10 3 m2 V 1 s 1) as shown in Fig. 28. Consequently, the mobility of the solvated electron either increases or decreases, respectively, as the electric field is increased [341— 348]. 

Fig. 28. Electric field dependence of the solvated electron drift mobility in liquid ethane at various temperatures (K). After Doldissen et al. [348].

---