Drift velocity, electron

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...

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. 

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. 6.18. Results from the positron-drift experiments of Paul and coworkers. The full curve is v+/(Zefj), obtained from a fit to all the data see text for details. Electron drift velocities (+) are shown for comparison on the left-hand scale. The points to the right of the vertical broken line were taken from runs at molecular hydrogen pressures of 50 torr ( ), 25 torr (a) and 10 torr (o).

As shown in Figure 6.18, electron drift velocities below e/p = 1 Td (= 1017 V cm2) are at least four times larger than those for positrons. Bose, Paul and Tsai (1981) attributed this difference to higher momentum transfer cross sections for positrons than for electrons at very low (i.e. 

If W is the electron drift velocity in the direction of the electric field, the current density or amount of (unit) charge transport per square centimeter per second is n W. Since P is defined as the reaction rate coefficient per unit charge transport, it follows that... 

W cm. sec.-1 Mean electron drift velocity in the direction of the field X... 

The aforementioned EEDF permits one to correlate the reduced electric field and average electron energy, which is related to electron temperatrrre as (e> = l e, even for non-Maxwellian distributions. Such a relation can be derived, for example, from averaging the electron drift velocity in energy space (3 4) ... 

The smallness of the anisotropy -C is directly related to the smallness of the electron drift velocity with respect to the thermal velocity of plasma electrons. 

Also relations (3-67), (3-68), and (4.3.9) determine eleetron mobility /Ue, which is the coefficient of proportionality between the electron drift velocity wj and electric field ... 

Applications of the continuous coronas are limited by low cmrent and power, which results in a low rate of treatment of materials and exhaust streams. Increasing the corona power without transition to sparks becomes possible by using pttlse-periodic voltages. The pulsed corona is one of the most promising atmospheric-presstrre, non-thermal discharges. The streamer velocity is about 10 cm/s and exceeds by a factor of 10 the typical electron drift velocity in an avalanche. If the distance between electrodes is about 1-3 cm, the total time necessary for the development of avalanches, avalanche-to-streamer transition, and streamer propagation between electrodes is about 100-300 ns. Therefore, the voltage pulses of this... 

Streamer Propagation Velocity. In the framework of the model of an ideally conducting streamer chaimel (4-12), estimate the difference between streamer velocity (at Ur ratio of about 100) and electron drift velocity in the external electric field. 

Drescher M, Kaplan N, Dormann E (2006) Conduction-electron drift velocity measurement via electron spin resonance. Phys Rev Lett 96 037601... 

From the measured current density I/S we can determine the electron concentration n if we assume the electron drift velocity v. The drift velocity in various discharges can be found in Ref. 32. We usually find the value like I/S 0.2 k/cur, v 107 cm/sec and n %10 Vcm3. 

Field dependence of electron drift velocity Cyclotron resonance with uniaxial stress... 

One disadvantage of the low beta approach is the possibility of a runaway discharge. In order to avoid the microinstabilities associated with a large electron drift velocity V, it is desirable to keep this velocity less than 2-5 times the the ion sound velocity (V = y V ). 

The CO joining of the beta limit of 2% and the limit on electron drift velocity with the assumption of R/a 2, leads to the condition ... 

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