Q(NiI) and Q(FeI) production rates in comet 3I as a function of the heliocentric distance. Squares represent UVES measurements and triangles X-shooter measurements. The curves show the production rates of NiI (in red) and FeI (in blue), which were obtained by multiplying the sublimation rates of the Ni(CO)₄ and Fe(CO)₅ carbonyls by the effective emitting area of each species (see text). For the solid curves, the sublimation rates were computed assuming T = 280 r_h^−1/2. For the dotted red curve, the sublimation rate was computed assuming T = 237 r_h^−1/3 for Ni(CO)₄.