Ionization, Penning

Chief ionization processes Charge transfer Electron impact ionization Penning ionization Chief excitation processes Electron impact excitation Ion-electron radiative recombination... 

Ion-neutral reactions in plasmas are studied from the ion current to the wall. The relation between the wall current and the plasma composition is obtained by balancing the total production processes, e.g., electron-impact ionization. Penning reaction, ion-neutral reaction, etc., to the total loss processes, e.g., diffusion, volume recombination, ion-neutral reactions, etc. An example of the balance equation is given by Eq. 5 for an infinite cylinder of radius R, in which electrons are multiplied by electron-impact ionization and lost by diffusion. The example is carried through to obtain the general relation of wall currents to plasma composition. 

Because of their high internal electronic energy (see Table 1), many decay channels are available in collisions of electronically excited inert gas atoms with other species [102,103]. These include various nonreactive pathways such as ionization (Penning, associative, and dissociative), excitation transfer, dissociative excitation, as well as a "chemical" deactivation channel, namely excimer formation. 

PI, PIS Penning ionization [116, 118] Auger deexcitation of metastable noble-gas atoms 4. ... 

Penning ionization. Occurs through the interaction of two or more neutral gaseous species, at least one of which is internally excited ... 

Penmman-Zoph process Penning discharge Penning gauge Penning ionization... 

Figure 8. Photoelectron spectrum (PES) and Penning ionization electron spectrum (PIES) of nitric oxide radical. Average vibrational energy spacing of the first band amounts to 285 and 284 cm", respectively (104).

If the work function is smaller than the ionization potential of metastable state (see. Fig. 5.18b), then the process of resonance ionization becomes impossible and the major way of de-excitation is a direct Auger-deactivation process similar to the Penning Effect ionization a valence electron of metal moves to an unoccupied orbital of the atom ground state, and the excited electron from a higher orbital of the atom is ejected into the gaseous phase. The energy spectrum of secondary electrons is characterized by a marked maximum corresponding to the... 

Another interesting situation which demonstrates the role of solvation on cluster reactions, with particular relevance to identifying mechanisms of possible importance in the condensed phase, concerns the initiation of electron transfer reactions. Interesting examples include those initiated through Penning ionization.161... 

In order to record excitation spectra, the radical ions must first be thermalized to the electronic ground state, which happens automatically if they are created in condensed phase (e.g. in noble-gas matrices, see below). In the gas-phase experiments where ionization is effected by collision with excited argon atoms (Penning ionization), the unexcited argon atoms serve as a heat bath which may even be cooled to 77 K if desired. After thermalization, excitation spectra may be obtained by laser-induced fluorescence. 

Penniman-Zoph process, 19 400 Penning cold-cathode ionization gauges,... 

In Table 17 the relevant data from the most recent investigation144, which is also based on Penning ionization electron spectra, are summarized. The characteristic ionizations of... 

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