M. Agúndez, C. Bermúdez, C. Cabezas, G. Molpeceres, Y. Endo, N. Marcelino, B. Tercero, J.-C. Guillemin, P. de Vicente, and J. Cernicharo
discovered
The rich interstellar reservoir of dinitriles: Detection of malononitrile and maleonitrile in TMC-1
Astron. Astrophys. 688, Art. No. L31 (2024).
Both molecules were detected in the course of the QUIJOTE line survey of the dark cloud TMC-1 with the Yebes 40 m dish. Dicyanomethane or malononitrile was identified through four rotational transitions with modest S/N and partially resolved ¹⁴N HFS splitting and 4 ≤ J ≤ 10 and K_a ≤ 1. Other lines are heavily blended or have a lower S/N. Z-1,2-Dicyanoethene or maleonitrile was identified through four rotational transitions with modest S/N of which one displayed partially resolved ¹⁴N HFS splitting; one HFS line of another transition is shown as are some blended lines. The quantum numbers were 7 ≤ J ≤ 11 and K_a ≤ 1. The abundance ratio of dicyanomethane to Z-1,2-dicyanoethene is about 3.5. Related molecules with one CN replaced by CCH are more abundant by varying degrees, consistent with a CCH to CN ration in TMC-1 of about 10.

Contributor(s): H. S. P. Müller; 09, 2024