Effect of the inner boundary condition of the radiation transfer equation on emergent spectrum (top panel) and temperature structure (bottom panel) of a thin partially ionized hydrogen atmosphere (T_eff = 1.2 × 10⁶ K, B = 10¹⁴ G) with Σ = 10 g cm^-2, above the condensed iron surface (solid curves) and black-body surface (dashed curves). For comparison, the black-body spectrum with T = T_eff (dotted curve) and the diluted black-body spectrum (f_c = 1.6, D = 1.4^-4), with a Gaussian line representing the proton cyclotron line (E₁ = 0.63 keV, τ₁ = 8.5, σ₁ = 11 eV), and a half-Gaussian line (E₂ = 0.3 keV, τ₁ = 2.5, σ₁ = 150 eV) describing the absorption feature at energies higher than E_c,i (dash-dotted curve) are shown. That last curve fits the spectrum of the atmosphere above the condensed iron surface.