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 × 106 levels. We have simulated detailed spectra comprising more than 109 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.