Kinetic emission

In kinetic emission, at higher kinetic energy above a certain threshold energy the impact of an ion can cause the emission of an electron from an inner shell. The core-ionized atom may subsequently decay by an Auger decay, which leads to the emission of another electron. 

One can compensate for charging by using a so-called flood gun, which sprays low-energy electrons onto the sample. Charging can also be minimized by using a beam of atoms instead of ions as primary particles. In this case, kinetic emission of electrons is the only source of charging, if we ignore the low yields of secondary ions. 

At this time a few comments about the model of Parilis et al. is appropriate. Their theory predicts that no kinetic emission can occur up to a certain threshold energy the yield then increases linearly with energy until at higher energy the slope again changes and the yield finally becomes linear with velocity. The majority of experimental results appear to confirm these trends suggesting that there is some truth in the basic assumptions. 

If the sample under study is an insulator (e.g., an oxide-supported catalyst), the arrival of positively charged primary ions and the emission of electrons by either potential or kinetic emission leads to positive charging of the sample. This has two negative effects ... 

The term A/ i.vfa ) = NB,di8k/Misk is the kinetic emission efficiency, which depends only on the kinetics at the disk electrode. At the steady state. 

Figure 5. (a) Typical kinetic emission curve for XeF at 351 nm, produced by the pulse electron irradiation of 500 Torr of xenon and 0.50 Torr of SFj. (b) Transformed emission curve showing straight line analysis beginning at time t. (c) Integrated kinetic emission curve. 

Kinetic emission is believed to apply to M and formation under rare gas bombardment. As shown pictorlally in Fig. 11 a sputtered atom may... 

Figure 11 Kinetic emission mechanism of secondary ion formation (from Ref. 10).

Indeed, such spectra have been used as one source or evidence supporting the Kinetic Emission model for multiply charged positive atomic ions from elements lighter than Phosphorus (Joyes 1973). This mechanism, discussed in Section 3.3.2.4, concerns the formation of core holes via atomic collisions with multiply charged ions formed as a result of the de-excitation of these core holes when present in the sputtered atomic/ionic populations. Owing to the short lifetimes... 

In an attempt to simplify the foregoing discussions, only a select few models are covered. This starts, for historical reasons, with a brief overview of the Local Thermal Equilibrium model. This is covered in Section 3.3.2.I. The Bond Breaking model is then discussed in Section 3.3.2.2, followed by the Electron Tunneling model in Section 3.3.2.3. For completeness sake, the Kinetic Emission model is presented in Section 3.3.2.4 as this appears to be responsible for the production of multiply charged atomic ions from the elements hghter than Phosphoras. Although many other models have also been put forward, only these are covered as the latter three, in particular, represent those currendy accepted for the respective systems described. 

Kinetic emission model A model describing multiply charged atomic secondary ion emission... 

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