Evolution with UV photon fluence of the N–H (a), C–H (b) and C=O (c) normalised column density (filled circles). The normalisation factor is the corresponding initial column densities. The error arising due to baseline subtraction was taken into the error estimation. When the error bar is not visible, the error is within the size of the filled circle. The best fit to the data (red solid lines) is also shown. The estimated destruction cross-section (σ_d) and the asymptotic destruction (a₁) for NH₂CHO are also reported.