Elucidating the Formation of Ethynylbutatrienylidene (HCCCHCCC; X<sup>1</sup>A′) in the Taurus Molecular Cloud (TMC-1) via the Gas-phase Reaction of Tricarbon (C<sub>3</sub>) with the Propargyl Radical (C<sub>3</sub>H<sub>3</sub>)
The astrophysical journal. Letters