Computed chemical abundances and local FUV radiation field for dust-free isothermal wind models for T_K = 1000 K. Left panels: chemical abundances relative to total H nuclei. Right panels: local mean intensity of the FUV radiation field at various positions along the wind (position indicated on the curves). Photoionization thresholds of C, S, Si, Mg, and Fe are also indicated by gray, yellow, orange, black, and blue dashed lines, respectively. Row a: Class 0 model with Ṁ_w = 2 × 10⁻⁶ M_⊙ yr⁻¹ and M_* = 0.1 M_⊙. Row b: Class 0 model with a lower mass-loss rate Ṁ_w = 10⁻⁶ M_⊙ yr⁻¹ and same mass. Row c: Class I model, with lower accretion rate Ṁ_w = 10⁻⁷   M_⊙ yr⁻¹ but higher mass M_* = 0.5 M_⊙.