UV shielding efficiency of six abundant molecules: H₂O, C₂H₂, CH₄ (top) and HCN, CO₂, C₃ (bottom). H₂O and C₃ are powerful molecules to shield the gas, by reducing the photodissociation rate of most of the molecules by two to three orders of magnitude. On the contrary, CH₄ and HCN are not relevant for the mutual shielding. NH₃ is relatively unaffected by molecular shielding, as its cross section extends up to 225 nm.