Cross-sections for the interactions between photons and material particles
The eq. (5.9) is basic for the dynamics of the radiating gases, because it defines the variation law of the specific intensity I v and, on the other hand, it will be shown that all the other quantities, which give the radiative contribution to the transport of mass of the different species, momentum and energy, can be expressed by means of I v . It requires, however, that the expressions of the cross-section σab and σba for the interaction phenomena between radiation and material particles be determined: now a large number of interactions with all these particles is possible, but, fortunately, in most. of the problems interesting the Gasdynamics the interactions that are “dominant” for the phenomena to study are in number rather limited. These interactions will be considered separately, and first of all there will be investigated those corresponding to the processes in which no free electrons are involved, i.e. the electrons are bound to the nucleus both before and after the interaction (bound-bound processes); there will be considered later on the processes in which free electrons exist (bound-free; free-free processes).
KeywordsFree Electron Material Particle Radiative Recombination Effective Atomic Number Complex Atom
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