Equilibrium collisional ionization

The intra-cluster gas in clusters of galaxies is generally hotter and in collisional ionization equilibrium, and the continuum is dominated by bremsstrahlung, making the interpretation of at least the hydrogen-like and helium-like K-shell emission lines relatively straightforward, but they are comparatively weak and an accurate determination of the temperature(s) is critical. 

We fitted the combined data with model spectra based on the atomic data compiled by Raymond and Smith (1977). The model spectra employed here are both for collisional ionization equilibrium (CIE) and non-equilibrium ionization (NEI) models with cosmic abundances (Allen, 1977). Single Te spectrum for both models can not fit the data. Two components of different Te models can reproduce the data well for both models. The physical parameters obtained with CIE models are self inconsistent because the ionization parameter r ( the electron density n X the elapsed time t the after shock heating ) is about 1011cm 3sec which is too short by an order of magnitude for the CIE condition to be reached. 

Attainment of equilibrium downstream of flame fronts makes it possible to use flames as media for studying high-temperature thermodynamics. Equilibrium may be approached via collisional ionization or chemi-ionization. When small concentrations of alkali metals are added to flames of low ion content, e.g., hydrogen or carbon monoxide flames, ions are produced by collisional reactions ... 

The temperatiue difference between electrons and heavy neutral particles due to Joule heating in the collisional weakly ionized plasma is conventionally proportional to the sqirare of the ratio of the electric field ( ) to the pressure p). Only in the case of small values of E/p do the temperatiues of electrons and heavy particles approach each other. Thus, this is a basic requirement for local thermodynamic equilibrium (LTE) in plasma. Additionally, LTE conditions require chemical equilibrium as well as restrictions on the gradients. The LTE plasma follows the maj or laws of equilibrium thermodynamics and canbe characterized by a single temperature at each point of space. Ionization and chemical processes in such plasmas are determined by temperature (and only indirectly by the electric fields through Joule heating). The quasi-equilibrium plasma of this kind is usually called thermal plasma. Thermal plasmas in nature canbe represented by solar plasma (Fig. 1-4). 

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