Sensitivity analysis of our model to the oxygen atom diffusion energy for CO₂ ice (dashed lines) and FA (suming c-t abundances). Values are represented with respect to H₂O column density- The difussion E_diff energy is defined from the E_diff/E_bin parameter in our models. E_diff/E_bin is set to 0.25, 0.30 and 0.40 in those models. The pale blue zone represents the observationally constrained abundances of CO₂ (Boogert et al. 2015; McClure et al. 2023) and the pale yellow zone represent the same for FA (Boogert et al. 2015; Rocha et al. 2024). We assume that FA and HCOO⁻ abundances sum.