Excited plasma temperatures density

Many sources of energy are used to excite samples to emit characteristic wavelengths for chemical identification and assay (91,92). Very high temperature sources can be employed but are not necessary. AH materials can be vaporized and excited with temperatures of only a few electron volts. The introduction of samples to be analyzed into high temperature or high density plasmas and thek uniform excitation often are problematic. 

Determination of Flame and Plasma Temperatures and Density Profiles by Means of Laser-Excited Fluorescence... 

Accordingly, an overpopulation of the argon metastable levels would explain both the overionization as well as the high electron number density in the ICP. Indeed, it may be that argon metastables act as ionizers, but at the same time are easily ionized [236]. This could explain the rather low interference caused by easily ionized elements, and the fact that ionic lines are excited very efficiently, despite the fact that their standard temperatures are much higher than the plasma temperatures. However, discrepancies are not encountered to such a great extent when the temperatures from the Saha equation are used in the calculations [237]. Nevertheless, a number of processes may be considered to predominate in well-defined zones of the plasma, as indicated by spatially resolved measurements of various plasma parameters [238]. 

Lx>ng radiative lifetimes of metastable states support the high density of these particles in slightly ionized plasma, or in excited gas. Thus, according to Fugal and Pakhomov [18, 19] the density of metastable atoms of helium at pressure of the order of a few Torrs, at temperatures ranging from 4 to 300 K, is about two orders of magnitude above the density of electrons. The density of metastable atoms and molecules in... 

Glow discharge or "cold" plasmas are gaining increased currency for the deposition of novel and potentially valuable macromolecular coatings. The range of properties attainable by a plasma-polymer is wide, and depends critically on such variables of the plasma deposition process as choice of monomer, substrate temperature (T ), power density (p), the excitation frequency (v), and others incluSing monomer flow rate, reactor geometry, etc... Control over these variables can produce crossllnked, dense deposits which adhere tenaciously to... 

At low temperatures a pure semiconductor is a perfect insulator with no free carriers. Upon laser irradiation at a frequency greater than the semiconducting band gap, a high density of electron-hole pairs can be excited which, at liquid-helium temperatures, condense into small droplets of electron-hole plasma. These electron-hole (e-h) droplets have been discussed thoroughly in a dedicated volume of Solid State Physics that contains reviews of theoretical aspects (Rice, 1977) and experiments (Hensel et al., 1977). 

Investigations on the doubly excited states of two electron systems under weakly coupled plasma have been performed by several authors. Such states usually occur as resonance states in electron atom collisions and are usually autoionizing [225]. Many of these states appear in solar flare and corona [226,227] and contribute significantly to the excitation cross-sections required to determine the rate coefficients for transitions between ionic states in a high temperature plasma. These are particularly important for dielectronic recombination processes which occur in low density high temperature plasma, occurring e.g. in solar corona. Coronal equilibrium is usually guided by the balance between the rates of different ionization and... 

There is another approach which can be used in suitable circumstances. Developed by Kowalik and Kruger (31), it involves measuring the population of an excited atomic state by LIFS. If the ground state population is known to be uniform in the flow field, then information about temperature can be inferred. They have used the method to measure electron number density in MHD plasma flows. 

Besides volume processes wall collisions of hydrogen particles can contribute to the vibrational population. A direct process is the interaction of already vi-brationally excited molecules with the surface (v) +wall —> ff2(w) mostly depopulating the vibrational levels. Further fundamental mechanisms are the Langmuir-Hinshelwood and the Eley-Rideal mechanism. They are based on recombining hydrogen atoms or ions Hads/gas + Hads —> H2(v). In the first case an adsorbed particle at the surface recombines with another adsorbed particle (Langmuir-Hinshelwood mechanism). In the second case one particle from the gas phase recombines with an adsorbed particle (Eley-Rideal mechanism). For these processes the data base is scarce and often not determined from plasma material interaction experiments. A dependence on particle densities, surface material and surface treatment as well as surface temperature can be expected. 

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