Formation and Spectroscopy of Dicyanotriacetylene (NC<sub>8</sub>N) in Solid Kr

Thermally induced creation of dicyanotriacetylene (NC<sub>8</sub>N) was observed in solid krypton. Samples were obtained by cryogenic trapping of gaseous cyanoacetylene/Kr mixtures subjected to electric discharges. Strong a <sup>3</sup>Σ<sup>+</sup><sub>u</sub> <i>→ </i>X <sup>1</sup>Σ<sup>+</sup><sub>g</sub> phosphorescence of NC<sub>8</sub>N 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 (C<sub>2</sub>), and these may serve as indispensable building blocks in the NC<sub>8</sub>N 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.