Left: depth into the disk to which UV can destroy CO₂ at a rate of 10⁻¹¹ s⁻¹ for a disk with an upper disk gas-to-dust ratio of 1000 and large grains (cyan) and small grains (blue). The black and grey contours show the area from which 25% and 75% of the emission of ¹² CO ₂ and ¹³ CO₂ respectively originates. The green lines show the dust τ = 1 surface at 15 μm for the large grains (up to 1 mm, dark green) and small grains (up to 1 μm, light green) respectively. The UV photo destruction rate has a stronger dependence on the grain size distribution than this μm dust photosphere. Right: depth into the disk to which X-rays can destroy CO₂ at a rate of 10⁻¹¹ s⁻¹ for different stellar X-ray luminosities (L_X in erg s⁻¹ ). The black and grey contours show the area from which 25% and 75% of the emission of ¹² CO ₂ and ¹³ CO₂ respectively is coming from. The green line shows the dust τ = 1 surface at 15 μm for the large grains (up to 1 mm).