EEPs in the gas phase

All existing techniques of EEP detection may be divided into several groups spectral, calorimetric, chemical titration, electrical methods, and also a method of sensor detection. 

The method of exchange-luminescence [46, 47] is based on the phenomenon of energy transfer from the metastable levels of EEPs to the resonance levels of atoms and molecules of de-exciter. The EEP concentration in this case is evaluated by the intensity of de-exciter luminescence. This technique features sensitivity up to-10 particle/cm, but its application is limited by flow system having a high flow velocity, with which the counterdiffusion phenomenon may be neglected. Moreover, this technique permits EEP concentration to be estimated only at a fixed point of the setup, a factor that interferes much with the survey of heterogeneous processes associated with taking measurements of EEP spatial distribution. 

The sensitivity of these methods, however, is low and does not allow operations at low gas pressures. 

The calorimetric method of detecting EEPs is based on measurements of the thermal effect arising on surfaces featuring high efficiency of deexcitation. This technique was used for evaluating 02( A ) [31] of a 

High sensitivity is featured by the electrical methods used to detect EEPs. These are based on measuring small currents that occur in the course of selective ionization of EEPs, or currents of secondary emission of electrons or ions knocked by EEPs out of the surface of solid targets (if such emission is taking place). 

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