Selected JWST/NIRSpec spectra toward d203-506. The red spectrum corresponds to the ON source measurement, which includes emission from the background H II region and the Bar PDR. The intrinsic spectrum of d203-506 is the ON – f ⋅ OFF measurement (with f = 0.95 in blue and f = 1 in cyan). The scaling factor, f, is determined from the nebular He I recombination lines (see the main text). These spectra show NIR carbon lines (permitted and forbidden), [Fe II], and vibrationally excited H₂ and OH lines (Zannese et al. 2024), among other species (see Berné et al. 2024). However, NIR O I fluorescent lines are not detected in the ON–OFF spectrum. These FUV-pumped O I fluorescent lines appear in the ON spectrum and arise from predominantly atomic gas close behind the ionization front of the Bar (the Δ feature; Haworth et al. 2023; Peeters et al. 2024).