Effect of incoming radiation on the non-LTE spectrum of Xe at Te = 100   eV
  The effect of a diluted Planckian radiation field on a Xe gas at the electron temperature of 100 eV is investigated within the framework of a Collisional Radiative Model, using the HULLAC code. The atomic model spans 19 charge states, includes 20 375 configurations and contains more than 2 10^6 levels. We have simulated detailed spectra comprising more than 10^9 transitions with the Mixed UTA model. The radiation temperature Tr is varied from 0 to 1.5 Te. The dilution factor, D, applied to decrease the radiation field, is varied independently from 0 to 3 at fixed Tr = Te. In both cases, the average charge state Z* increases from 15 to 27, but in different ways. It is shown that even a dilution D = 0.01 changes Z* by more than 1.5. Different combinations of Tr and D yielding exactly the same Z*, may give line ratios sufficiently different to be observed. This fact is explained by the interplay of the shape of the radiation field and the atomic structure. 
Marcel Klapisch, Michel Busquet
physics.atom-ph astro-ph.SR