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Abstract:
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The atomic physics relevant to gaseous nebulae is critically examined using modelling
software with particular emphasis on radio recombination lines (RRLs). The
theoretical spectral line intensities can be deduced if we know the population structure
of the bound electrons in the gas under non-thermal equilibrium conditions.
The population structure of hydrogen is solved for various environments using a
capture-collision-cascade model that incorporates an ambient radiation eld.
The validity of assuming Case B (Baker & Menzel, 1938) for nebulae is investigated.
It is known that Case B is appropriate for levels with small principal quantum
numbers (n < 40), but this assumption is re-examined for high levels which are
relevant to RRLs.
E ects of an ambient radiation eld on the population structure is examined and
processes that are stimulated by a radiation eld are included in the model. This is
done as a preliminary investigation to extend the model to a photoionization code. |
