Ion impact

Hamdan M and Brenton A G 1991 HIgh-resolutlon translational energy speotrosoopy of moleoular Ions Physics of Ion impact Phenomena ed D Mathur (Berlin Springer)... 

Ions impacting onto the cathode during a discharge cause secondary electrons and other charged and neutral species from the electrode material to be ejected. Some of these other particles derived... 

As the electric field always points in the direction of the electrode, the densities of the electrons and negative ions are set equal to zero at the electrode. It is assumed that the ion flux at the electrodes has only a drift component, i.e., the density gradient is set equal to zero. The conditions in the sheath, which depend on pressure, voltage drop, and sheath thickness, are generally such that secondary electrons (created at the electrodes as a result of ion impact) will ionize at most a few molecules, so no ionization avalanches will occur. Therefore, secondary electrons can be neglected. 

Most of the electron and ion impact reactions that are included in this code are listed in Table II. Added to this are the elastic collisions SiHa -1- e [274] and H2 -f e [275], the recombination SiHJ + SiH 2SiH3 [214], and the charge exchange HJ -f H2 -1- H [193]. Note that disilane is not included. The... 

Optical emission is a result of electron impact excitation or dissociation, or ion impact. As an example, the SiH radical is formed by electron impact on silane, which yields an excited or superexcited silane molecule (e + SiHa SiH -t-e ). The excess energy in SiH is released into the fragments SiH SiH -I-H2 + H. The excited SiH fragments spontaneously release their excess energy by emitting a photon at a wavelength around 414 nm. the bluish color of the silane discharge. In addition, the emission lines from Si. H, and H have also been observed at 288, 656, and 602 nm, respectively. 

Now, we consider H, atoms produced from hydrogen molecules adsorbed on zinc oxide under the influence of electron (ion) impact. We suppose that in this case the energy released in interaction of an electron (ion) with an adsorbed molecule is enough to break any bond between hydrogen atoms. As a consequence, Hj atoms bounce apart over the surface. Hydrogen atoms produced in this case are similar to H atoms adsorbed on the oxide surface from the gas phase at small surface coverages. In other words, they can be chemisorbed as charged particles and thus may influence electric conductivity of zinc oxide. This conclusion is consistent with the experimental results. 

The time-of-flight secondary ion mass spectrum of a thick film prepared from Si(OEt)4 on a hydrophilic silicon substrate (Fig. 1) reveals a distribution of masses up to 1200 amu. The observed formation of cationized oligomers with a distribution shown in Fig. 1 can be explained by bond cleavage within the uppermost monolayer of the polycondensate of TEOS as a result of primary Ar+ ion impact. 

SIMS involves bombarding a material surface with a primary ion beam, with a typical energy in the keV range. Ion impacts on the surface induce a so-called collision cascade sputtering process, where the energy of the primary ions is transferred to the surface through nuclear collisions [Brunelle et al. 2005]. 

TWO-CENTER EFFECTS IN IONIZATION BY ION-IMPACT IN HEAVY-PARTICLE COLLISIONS... 

Figure 20. Electron emissions at 0 = 0° for 40-keV H+ ion impact in H2. The double differential cross section (DDCS = ifia/dfldE ) is plotted against k/v, where v is the impact velocity, k is the ejected-electron momentum, and dU — 2k sin 0 dd. The filled circles represent the experimental data [38], and the CDW-EIS results are given by the solid line [38].

Figure 22. Electron emissions for 40-keV H+ ion impact on He. A CDW-EIS surface plot [38] for the double differential cross section d2a/dfidEk is plotted against k/v (see the caption of Fig. 20).

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