Electron attachment rates

Electron attachment rates have been measured for numerous solutes. Many of these studies were limited to three solvents cyclohexane, 2,2,4-trimethylpentane, and tetrame-thylsilane (TMS), and those rates are discussed here. What to expect in other liquids can be inferred from these results. Considerable insight has been gained into certain reactions. Equilibrium reactions of electrons are particularly interesting since they provide information not only on energy levels, as mentioned above, but also on the partial molar volume of trapped electrons. This has led to a better understanding of the mechanism of electron transport. 

In nonpolar liquids, bimolecular electron attachment rate constants, k , are much larger than those for conventional reactions of ions or radicals. This is, in part, related to the high mobility of electrons in these liquids but various other factors, like Vq, the kinetic energy of the electron, and dipole moment of the solute, are important as well. These and other factors are examined below the dependence of on the energy gap, AGr, in representative liquids is also shown and discussed. 

The use of the weakly bound electron in a Rydberg atom to measure low energy electron attachment rate constants has proven to be one of the more useful applications of Rydberg atoms. Measurements have been refined to the point of measuring the lifetimes of negative ions formed by attachment,96 and it is likely that further developments will follow. 

The EA of the isolated molecules are probably negative for the former, but they are large and jijC itive for the latter the for the former are most likely <10 sec, but they are >10 sec for the latter the thermal electron attachment rates, for the former are orders of magnitude smaller compared to those for the latter. 

Figure 7. Total electron attachment rates as a function of mean electron energy, and swarm-unfolded electron attachment cross sections as a function of electron energy for CcFe (30) and CeFsCF, (19)...

Table 9. Positions of electron attachment cross section maxima, values of o ( e) at these maxima, energy integrated cross sections, and thermal electron attachment rates for haloethanes...

The value of the radius, R, used is 1 nm, p is the density in g/cm. The value of the rate constant at high pressure is below the theoretical diffusion rate, however it is actually at or above the maximum value expected for electron attachment rates. Warman predicted that electron attachment rate constants are not expected to exceed 3 X 10 That rate constant corresponds, in the units used... 

The electron attachment rate is basically the cross section times the velocity (see equation (2.14)). For attachment rates to a neutral target, since the cross section varies as 1 /E1/2 = 1/v, this means that the attachment rate tends asymptotically to a constant value. Thus, for SF6,... 

The electron attachment rate constant for SFg in nitrogen at ambient temperature and pressure showed a smooth decline with increasing E/N over the range of 0.39-0.78 Td [56]. As shown in Figure 13.7, the results obtained by IMS agree closely with those obtained by the well-established high-pressure swarm technique [57]. A further series of experiments with E/N from 0.05 to 0.9 Td confirmed this excellent agreement between the two methods [55]. 

Mayhew, C.A. Critchley, A.D.J. Howse, D.C. Mikhailov, V. Parkes, M.A. Measurements of thermal electron attachment rate coefficients to molecules using an electron swarm technique. Eur. Phys. J. D 2005,35, 307-312. 

Tabrizchi, M. Abedi, A. A novel use of negative ion mobility spectrometry for measuring electron attachment rates. J. Phys. Chem. A 2004,108, 6319-6324. 

Fig. 5. Electron attachment rate constants for NF3 as a function of the mean electron energy, from [13].

FIGURE 3 Total electron-attachment rate constant as a function of the mean electron energy s) for the perfluoroalkanes CA/F2A/+2 (N= -6) and their dc uniform field breakdown voltages relative to SFe. [From Christophorou, L. G., et al. (1984), IEEE Trans. Elect. Insul. El-19, 550-566.]... 

Goulay F, Rebrion-Rowe C, Carles S, Le Garrec JL, Rowe BR. (2004) The electron attachment rate coefficient of HI and DI in uniform supersonic flow. J. Chem. Phys. 121 1303-1308. 

Figure 24 Electron attachment rate to SFg as a function of electric field in liquid propane. (Redrawn from the data of Bakale, G., and Schmidt, W.R, Z. Naturforsch., 36a, 802, 1981.)...

Figure 9 Electron attachment rate as a function of Vq. T, SF , CCI4 , N2O 0,02 o, ethyl-Br.

Fig. 20. Electron attachment rate constant versus the mean...

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