SIMBAD references

We present a joint crossed molecular beam and kinetics investigation combined with electronic structure and statistical calculations on the reaction of the ground-state cyano radical, CN(X ²Σ⁺), with the 1,3-butadiene molecule, H₂CCHCHCH₂(X ¹ A_g), and its partially deuterated counterparts, H₂CCDCDCH₂(X ¹ A_g) and D₂CCHCHCD₂(X ¹ A_g). The crossed beam studies indicate that the reaction proceeds via a long-lived C₅H₆N complex, yielding C₅H₅ N isomer(s) plus atomic hydrogen under single collision conditions as the nascent product(s). Experiments with the partially deuterated 1,3-butadienes indicate that the atomic hydrogen loss originates from one of the terminal carbon atoms of 1,3-butadiene. A combination of the experimental data with electronic structure calculations suggests that the thermodynamically less favorable 1-cyano-1,3-butadiene isomer represents the dominant reaction product; possible minor contributions of less than a few percent from the aromatic pyridine molecule might be feasible. Low-temperature kinetics studies demonstrate that the overall reaction is very fast from room temperature down to 23 K with rate coefficients close to the gas kinetic limit. This finding, combined with theoretical calculations, indicates that the reaction proceeds on an entrance barrier-less potential energy surface (PES). This combined experimental and theoretical approach represents an important step toward a systematic understanding of the formation of complex, nitrogen-bearing molecules–here on the C₅H₆ N PES–in low-temperature extraterrestrial environments. These results are compared to the reaction dynamics of D1-ethynyl radicals (C₂D; X ²Σ⁺) with 1,3-butadiene accessing the isoelectronic C₆H₇ surface as tackled earlier in our laboratories.