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 T_r is varied from 0 to 1.5 T_e. The dilution factor, D, applied to decrease the radiation field, is varied independently from 0 to 3 at fixed T_r = T_e. 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 T_r 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.