Photochemistry of Diacetylene

Article abstract of DOI:10.1021/j100286a036

Adsorption coefficients of C4H2 have been measured in the 183-260-nm wavelength region.The photochemistry of diacetylene has been studied at 147.0, 184.9, 228.8, and 253.7 nm.The primary dissociative processes at 147 nm, deduced from the photolysis of C4H2 and D2 mixtures, are, in order of decreasing importance, C4H2 + hν -> C4H + H, C4H2 + hν -> C2H2 + C2, and C4H2 + hν -> 2C2H with quantum yields of 0.2, 0.1, and 0.03, respectively.In addition, the quantum yields of products and of reactant disappearance were measured in neat C4H2 and C4H2 and N2 mixtures.It is concuded that (1) reactions involving metastable excited states, C4H2^** + C4H2 -> C8H2 + H2, are the main disappearance processes at three other wavelengths and (2) the C4H2^** sates are stable toward collisions with N2.The excited-state reactions may be the predominant photochemical processes of C4H2 in Titan's stratosphere.