Electron attachment cross section

This expression can be generalized in the presence of an external field, and the ratio of the escape probability as a negative ion to that as an electron in the absence of a scavenger computed as a function of the external field. From such an analysis and taking L = 4 A, a typical intermolecular separation, Mozumder and Tachiya obtained electron attachment cross sections in NP as 4 x 10-16,5 X 10 17, and 1 X 1CF18 cm2, respectively, for SF6, CC14, and CS2 with -15% uncertainty. 

Fig. 11.17 Cross sections for Rydberg electron ( ) (ref. 78) and free electron (O) (ref. 80) attachment to C5F8, 1,1 1-C2C13F3, CC13F,SF6, and CCI4. The Rydberg electron attachment cross sections are calculated using Eq. (11.42) (from ref. 78).

It is interesting to note the structure in the total electron attachment cross section o (e) below M eV in Fig. 5, which indicates the existence of tSree NISs in this energy range. Since at thermal and epithermal energies the ions formed are long-lived and the measured attachment rates showed ( 8, ] ) no pressure... 

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 gas-phase ion chemistry of COCIF has been studied by ion cyclotron mass spectrometry, and the relative abundance of the primary negative ions X , [Xj] and [XCO] (X = F or Cl) formed by electron impact was measured. The electron energy dependence of the dissociative electron attachment cross-sections for the negative ion formation was determined [1071,1073],... 

The adsorbate substrate complex excitation mechanism predicts an action spectrum analagous to the absorption spectra of the complex. The direct mechanism predicts a photochemical action spectrum similar to that of the gas phase molecule. The final mechanism, dissociative electron attachment (DEA), suggests that the action spectrum should be referenced to the absorbance of the substrate, modified by the surface work function and electron attachment cross section of the adsorbate. The DEA mechanism appears to be of importance for many metal and semiconductor substrates, especially for the case of photochemistry induced by anomalously low energy radiation. 

If the photon energy is greater than the work function, O, of the adsorbate covered surface then free electrons will be generated. If the electrons, or a sub-population of them, are resonant with the electron attachment cross section of the adsorbate then reaction may occur on the ionic potential surface many molecules are unstable to electron attachment in the gas phase. In many cases the electron attachment cross section is peaked at low energies, so photoinduced electron reactions are... 

Figure 5 (Kurachi and Nakamura, 1990) presents a survey of electron collision cross sections of CF4. In addition to the momentum-transfer cross section q , it shows the vibrational-excitation cross sections q T, and q (for two different vibrational modes), the (total) electronic-excitation cross section q, the dissociation cross section q j , the electron-attachment cross section qg, and the (total) ionization cross section 9,. Each of the cross sections is a function of the electron kinetic energy and reflects the physics of the collision process, which is being clarified by theory. The cross sections designated as total can be discussed in greater detail in terms of different contributions, which are designated as partial cross sections.

Buchel nikova (1959) performed a direct measurement of the electron attachment cross section for energies between 0 and 1 eV using an electron beam apparatus. 

Regardless which model one wants to adopt for the Ps formation process, it is clear that factors such as ionization and excitation potentials, electron attachment cross sections, the... 

FIGURE 1 Ionization cross section o-/(e) for N2 and SFe close to the ionization onset /. Electron-scattering cross section as a function of e for N2 and electron-attachment cross section cra(s) for SF0. Normalized electron energy distribution function E/N) as a function of s for N2 at two values of E/N. [From Christophorou, L. G., et al. 

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