Formation and Spectroscopy of Dicyanotriacetylene (NC₈N) in Solid Kr

Thermally induced creation of dicyanotriacetylene (NC₈N) was observed in solid krypton. Samples were obtained by cryogenic trapping of gaseous cyanoacetylene/Kr mixtures subjected to electric discharges. Strong a ³Σ⁺_u → X ¹Σ⁺_g phosphorescence of NC₈N is reported here for the first time; its vibronic structure permitted the measurement of several ground-state vibrational frequencies. Other chemical species, mostly smaller than the precursor molecule, have also been formed, among them the dicarbon molecule (C₂), and these may serve as indispensable building blocks in the NC₈N synthesis. Processes leading to the elongation of cyanoacetylenic chains are of potential importance for the chemistry of icy grains present in the interstellar gas clouds.