SIMBAD references

We report the first detection in space of the single deuterated isotopologue of methyldiacetylene, CH₂DC₄H. A total of 12 rotational transitions, with J = 8-12 and K_a = 0 and 1, were identified for this species in TMC-1 in the 31.0-50.4 GHz range using the Yebes 40m radio telescope. The observed frequencies allowed us to obtain, for the first time, the spectroscopic parameters of this deuterated isotopologue. We derived a column density of (5.5 ±0.2) x 10¹¹ cm^–2. The abundance ratio between CH₃C₄H and CH₂DC₄H is 24 ±2. This ratio is similar to that found for the CH₃C₃N/CH₂DC₃N analogue system, which is 22 ±2. We did not detect the deuterated species CH₃C₄D, which has already been observed in laboratory experiments. The detection of deuterated CH₃C₄H allows us to extend the discussion on the chemical mechanisms of deuterium fractionation at work in TMC-1 using a new gas-phase chemical model with multiply deuterated molecules. Introducing a possible deuterium exchange reaction between CH₃CCH and atomic deuterium allows us to account for the CH₃C₄H/CH₂DC₄H abundance ratio.