Observed integrated line areas of MgC₃N, MgC₄H, MgC₅N, and MgC₆H toward IRC +10216 in the Q-band, and the rotational diagram for each molecule built from those integrated areas, together with the best fits that provide an estimation of their column densities and rotational temperatures. The dotted curve in the top panel is the noise level achieved in our survey across the whole frequency range. A few lines beyond 44 GHz are below the detectability limit and for this reason they do not appear in Table 1.