Time evolution of [CO] (gas [dotted] and ice [solid] phases) (top left). The remaining panels show the equivalent panels for the gas phase abundances of the rest of the species for the overall best fitting model (ζ = 2.2 × 10⁻¹⁷ s⁻¹), for the XR search of the P2 clump, that is with n_H = 1.0 × 10⁵ cm⁻³, A_v = 20 mag and T = 15 K. The time of the best overall model along each of these tracks is marked with a ‘+’ symbol. Horizontal dotted lines show the observed values of abundances, with the uncertainties shown by the shaded bands.