Level populations of hydrogen atoms affected by radiation fields. The departure coefficients b_n varying with principal quantum number n affected by different radiation fields are plotted in the top panel. The amplification coefficients β_n,n+1 influenced by different radiation fields are presented in the middle panel. The corresponding intensities of mean radiation field ∫ J_vϕ_vdv and the saturation intensity J_s are shown in the bottom panel. The electron temperature is T_e = 10 000 K, and the electron density is n_e = 10⁶ cm⁻³.