A Combined Experimental and Theoretical Study on the Formation of Interstellar C 3 H Isomers

The reaction of ground-state carbon atoms with acetylene was studied under single-collision conditions in crossed beam experiments to investigate the chemical dynamics of forming cyclic and linear C3H isomers (c-C3H and l-C3H, respectively) in interstellar environments via an atom-neutral reaction. Combined state-of-the-art ab initio calculations and experimental identification of the carbon-hydrogen exchange channel to both isomers classify this reaction as an important alternative to ion-molecule encounters to synthesize C3H radicals in the interstellar medium. These findings strongly correlate with astronomical observations and explain a higher [c-C3H]/[l-C3H] ratio in the dark cloud TMC-1 than in the carbon star IRC+10216.