Fine-Structure Ratios of Hydrogen-Like Iron Ly α in High-Temperature Plasmas

The relative intensity of the hydrogen-like (Fe XXVI) Ly α lines fine-structure components, 2p^2P_1/2 →1s^2S_1/2 and 2p^2P_3/2 →1s^2S_1/2 is commonly assumed to be fixed at a 2:1 ratio derived from the statistical weights of the upper states when interpreting astrophysical X-ray spectra. However, recent astrophysical observations suggest departures from this expectation, indicating sensitivity to plasma conditions or the effect of the material the light must travel through to reach the observer. To explore this, we employ the GSM collisional-radiative code using fine structure resolved atomic data calculated by the Los Alamos National Laboratory Atomic Data Codes to calculate this ratio for H-like Fe XXVI across a broad temperature range (10⁶ - 10⁹ K), with consideration of density effects. Our goal is to assess how these parameters modify the ratio and to potentially provide more accurate diagnostics for high-temperature astrophysical plasmas. We present the results of the ratios under various ranges of temperature and electron density.