Azimuthally averaged radial profiles of the [C I], HCN, CN, C₂H, NO, and HCO⁺ emission predicted by models with a gas gap depth of one (no gap; dark red), 10⁻¹ (orange), 10⁻² (pink), 10⁻³ (purple), 10⁻⁴ (blue), and 10⁻⁵ (very deep gap; light blue). The C₂H emission is increased by a factor of 50 for all models to show it on the same scale as the observations. The peak C₂H intensity of the full disk model is 2 mJy km s⁻¹ beam⁻¹. The small dust density is dropped by the same factor in the gap. The observed intensities are indicated with the black lines.