Magnesium radicals MgC$_5$N and MgC$_6$H in IRC+10216
  After the previous discovery of MgC$_3$N and MgC$_4$H in IRC+10216, a deeper
Q-band (31.0-50.3 GHz) integration on this source had revealed two additional
series of harmonically related doublets that we assigned on the basis of
quantum mechanical calculations to the larger radicals MgC$_5$N and MgC$_6$H.
The results presented here extend and confirm previous results on
magnesium-bearing molecules in IRC\,+10216. We derived column densities of
(4.7$\pm$1.3)$\times$10$^{12}$ for MgC$_5$N and (2.0$\pm$0.9)$\times$10$^{13}$
for MgC$_6$H, which imply that MgC$_5$N/MgC$_3$N=0.5 and MgC$_6$H/MgC$_4$H =
0.9. Therefore, MgC$_5$N and MgC$_6$H are present with column densities not so
different from those of the immediately shorter analogs. The synthesis of these
large magnesium cyanides and acetylides in IRC+10216 can be explained for their
shorter counterparts by a two-step process initiated by the radiative
association of Mg$^+$ with large cyanopolyynes and polyynes, which are still
quite abundant in this source, followed by the dissociative recombination of
the ionic complexes.
