Electron Elastic-Scattering Cross-Section

In the e + M case, a very sensitive Indicator of shape resonance behavior Is the vibrational excitation channel. Vibrational excitation Is enhanced by shape resonances (3,17), and Is typically very weak for non-resonant scattering. Hence, a shape resonance, particularly at Intermediate energy (10-40 eV) (41,50), may be barely visible In the vlbratlonally and electronically elastic scattering cross section, and yet be displayed prominently In the vlbratlonally Inelastic, electronically elastic cross section. 

NIST Electron Elastic-Scattering Cross-Section Database (SRD 64) [35]... 

Figure 3.2.3.12 Comparison of differential elastic-scattering cross sections, dcr/d 2, calculated from the DHF potential (solid lines) from the NIST Electron Elastic-Scattering Cross-Section Database [35] for argon with measured differential cross sections (symbols) [105-108] for electron energies of (a) 50 eV and (b) lOOOeV [97].

Jablonski, A., Salvat, F., and Powell, C.J. (2010) NIST Electron Elastic-Scattering Cross-Section Database, Version 3.2, Standard Reference Data Program Database 64, U.S. Department of Commerce, National Institute of Standards and Technology, Gaithersburg, MD, http Ifwww. nist.gov/srd/nist64.cfm. (accessed November, 2011). 

The ratio of elastically to inelastically scattered electrons and, thus, their importance for imaging or analytical work, can be calculated from basic physical principles consider the differential elastic scattering cross section... 

Being formed in the gaseous phase medium, the electronically excited particles (EEPs) reach the solid surface by diffusion. The diffusion coefficients of EEPs are, as a rule, smaller than the self-diffusion coefficients of parent gas, a factor that is associated with increasing of the EEP elastic scattering cross-section at parent molecules due to the redis-... 

If we assume that rj is small, %. ft, ft, Q) = -a, and the total electron-perturber elastic scattering cross section is given by... 

As the positron energy is raised above the positronium formation threshold, EPs, the total cross section undergoes a conspicuous increase. Subsequent experimentation (see Chapter 4) has confirmed that much of this increase can be attributed to positronium formation via the reaction (1.12). Significant contributions also arise from target excitation and, more importantly, ionization above the respective thresholds (see Chapter 5). In marked contrast to the structure in aT(e+) associated with the opening of inelastic channels, the electron total cross section has a much smoother energy dependence, which can be attributed to the dominance of the elastic scattering cross section for this projectile. 

If elastic scattering is the only open channel (except for electron-positron annihilation with its very small cross section), the total and elastic scattering cross sections are identical, and the cross section may be calcu-... 

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