Unimolecular decomposition of chemically activated singlet and triplet D3-methyldiacetylene molecules

The reaction dynamics of the dicarbon molecule with D3-methylacetylene, CD3CCH(X1A1), were investigated utilizing the crossed molecular beams approach. By combining the experimental results on the atomic hydrogen versus deuterium loss channels with electronic structure calculations, we could substantiate that the D3CCCCC(X2A) radical is neither formed on the singlet nor on the triplet surface. Secondly, the isotopic studies showed explicitly that on the triplet surface, only the 2,4-pentadiynyl-1 radical – detected via its isotopomer [C5HD2(X2B1); HCCCCCD2] – was synthesized. On the singlet surface, both the 2,4-pentadiynyl-1 [C5HD2(X2B1), HCCCCCD2] and 1,4-pentadiynyl-3 radical [C5HD2(X2B1) HCCCDCCD] can account for the experimental data.