Penning ionization impact

Secondly, the cross section reflects the nature of the dependence of the partial widths on the intermolecular distance R. As expected from Eq. (20), is small for large R and increases gradually with decrease in R. On the other hand, Fgx in its empirical form (Eq. (17)) is extremely small at large distances and increases sharply near the repulsive wall. Therefore, the de-excitation probability due to Penning ionization is determined by the dipole-dipole part of the decay width in collisions with large impact parameter, whereas the probability for Penning ionization is already almost unity by the single contribution... 

We will now review the studies of intramolecular Penning ionization and multiple scattering/ionization in vdW clusters, followed by our own electron impact studies on argon/methanol heteroclusters. 

Table 5. Vibrational Distributions of NO (A) in the HeJ/NO Charge-Transfer, Electron-Impact Ionization, Photoionization, He(2 S)/NO Penning Ionization, Franck-Condon Factors for the NO(X) —> NO (A) Ionization...

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

Among the possibilities available to postionize sputter-ejected neutral surface particles, electron impact ionization has been employed in a variety of experimental approaches. More recently, photoionization by resonant or nonresonant multiphoton absorption processes has been established as another very effective technique in SNMS. Other processes as Penning ionization or charge exchange play only a minor role in postionization for SNMS. 

Figure 3.10 Penning ionization of a bandgap solid by metastable He (He ) impact. The energy released by the transition of a valence electron to the Is state ( ) excites the 2s electron of He to the state above the vacuum...

Two other groups of processes in which electron emission from quasimolecules takes place are Penning ionization and transfer ionization processes. However, they are different from those discussed here in that the electronic energy of the collision system in the initial state is high enough for an ionization process to occur. This leads to ionization even at large impact parameters and very low kinetic collision energies. For a more detailed discussion the reader is referred to recent review articles. ... 

When sample aerosol (see below) is introduced into an ICP, the droplets are desolvated, molecules are broken down into the constituting atoms and these are ionized via electron impact and Penning ionization (ionization as a result of energy transfer from an excited Ar atom). Although an ICP is not in thermal equilibrium, its ionization efficiency can be decently estimated on the basis of the Saha equation [5] ... 

Ionization The formation of ions, generally by electron-atom/molecule impact. Other processes, such as Penning ionization, can also cause ionization. 

Penning (metastable) Ionization Figure 5 Electron impact and Penning (metastable) ionization processes. 

The electron impact ionization does not occur in the cascade arc torch, and the energy transfer between excited neutrals of the carrier gas and the added gases becomes the dominant mechanism, i.e., the Penning-type reaction or resonance... 

Penning ioni2ation electron spectroscopy is also called (i) metastable atom electron spectroscopy (MAES), (ii) metastable deexdtation spectroscopy (MDS), (iii) metastable quenching spectroscopy (MQS), and (iv) metastable impact electron spectroscopy (MIES), where atom at metastable state is used instead of photon to ionize the target material When a slow, long-lived, electronically excited metastable atom hits a solid surface, most of its excitation energy is used to eject electrons from the surface. Unlike photons used for UPS, metastable atoms do not penetrate into the bulk of the solid. PIES, therefore, excites the outermost surface layer selectively (39). 

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