J. Cernicharo, C. Cabezas, J. R. Pardo, M. Agúndez, O. Roncero, B. Tercero, N. Marcelino, M. Guélin, Y. Endo, and P. de Vicente
reported on the
The Magnesium Paradigm in IRC +10216: Discovery of MgC4H+, MgC3N+, MgC6H+, and MgC5N+
Astron. Astrophys. 672, Art. No. L13 (2023).
The molecules were identified in the course of a molecular line survey with the 40 m Yebes radio telescope between 31.0 and 50.3 GHz. All identifications relied on quantum chemical calculations in the absense of Laboratory spectroscopic data. Seven successive, unblended transitions with 11 ≤ J“ ≤ 17 were identified for MgC₄H⁺. In addition, nine successive transitions with 25 ≤ J” ≤ 33 were identified between 72.4 and 95.6 GHz in data of an IRAM 30 m molecular line survey; two transitions were partly blended. 16 transitions with 26 ≤ J“ ≤ 41 were accessed in the case of MgC₆H⁺. Four transitions were partly blended, one was blended heavily. Seven successive transitions with 11 ≤ J” ≤ 17 were identified for MgC₃N⁺ of which five were partially blended. 16 transitions with 27 ≤ J“ ≤ 42 were accessed in the case of MgC₅N⁺. Nine were partially blended, one heavily, and two lines were too week to be detected securely. The rotational temperatures are around 20 K; the value of ~10 K for MgC₃N⁺ should probably be viewed with great caution. The abundance ratios are about 48 : 12 : 25 : 11 for MgC₄H⁺, MgC₃N⁺. MgC₆H⁺, and MgC₅N⁺, respectively. The cations are about a factor of 200 less abundant than their neutral counterparts in the case of MgC₄H⁺ and MgC₆H⁺, whereas is is about a factor of 100 for MgC₃N⁺ and about a factor of 50 for MgC₅N⁺. Again, the ratios for MgC₃N⁺ should be viewed with caution.

Contributor(s): H. S. P. Müller; 05, 2023