J. Cernicharo, C. Cabezas, J. R. Pardo, M. Agúndez, C. Bermúdez, L. Velilla-Prieto, F. Tercero, J. A. López-Pérez, J. D. Gallego, J. P. Fonfría, G. Quintana-Lacaci, M. Guélin, and Y. Endo
reported on the
Discovery of two new magnesium-bearing species in IRC+10216: MgC₃N and MgC₄H
Astron. Astrophys. 630, Art. No. L2 (2019).

The 40 m Centro Astronómico de Yebes dish and the IRAM 30 m dish were employed to observe 22 rotational transitions of magnesium monodiacetylide, MgC₄H, between 33 and 111 GHz toward the famous near-by carbon-rich AGB star CW Leonis. The authors label 8 transitions between 71 and 108 GHz as observed with two fine structure components and one with one. The astronomical data were employed to derive spectroscopic parameters in the absence of laboratory data.

The authors also present a confirmation of the detection of magnesium monoacetylide, MgC₂H. Eight transitions with N' = 9 to 16 between 89 and 169 GHz were shown. Two transitions (N' = 9 and 10) are clearly visible with two fine structure components. One component of the N' = 11 transition appears to be not or only slightly blended. The remainder of the lines are difficult to asses without modeling results because of blending or poorer signal-to-noise ratios.

M. Agúndez, J. Cernicharo, and M. Guélin
had earlier reported on
New molecules in IRC +10216: confirmation of C₅S and tentative identification of MgCCH, NCCP, and SiH₃CN
Astron. Astrophys. 570, Art. No. A45 (2014).

J. R. Pardo, C. Cabezas, J. P. Fonfría, M. Agúndez, B. Tercero, P. de Vicente, M. Guélin and J. Cernicharo reported on
Magnesium Radicals MgC₅N and MgC₆H in IRC +10216
Astron. Astrophys. 652, Art. No. L13 (2021).
The 40 m Centro Astronómico de Yebes dish was employed to observe 16 rotational transitions of magnesium monotriacetylide, MgC₆H, with N“ = 26 to 41 between 31.0 and 50.3 GHz toward the famous near-by carbon-rich AGB star CW Leonis. Some of the transitions displayed resolved fine structure (FS) splitting. 10 transitions appear to be unblended or only slightly blended, one FS component each was sufficiently clear for two more transitions. The identification of a new species is unambiguous. The identification of the carrier may be viewed with slight caution in the absence of laboratory data. However, the FS spltting is a very strong indicator that the identification is unambiguous as well. It is very interesting to note that the triacetylide and the diacetylide have about the same column densities, and both are about a factor of 10 more abundant than MgC₂H. The authors justified this by their likely formation which involves radiative association reactions of Mg⁺ with C_2nH₂. These ratios are quite similar to those observed for the isoelectronic MgC_2n+1N molecules.

Contributor(s): H. S. P. Müller; 10, 2019; 09, 2021