THE ABSORPTION SPECTRUM OF CNC

Abstract

The ultraviolet absorption spectrum of the free CNC radical has been discovered in the flash photolysis of diazoacetonitrile, HC(CN)N2. The identity of the radical has been proved from isotopic evidence, using 15N and 13C, together with rotational analysis of the bands. Rotational analyses have shown that the bands of CNC must be assigned to two electronic transitions, A2Δu–X 2Πg, and [Formula: see text]. The sequence bands in the bending vibrations, which are observed in both electronic transitions, show evidence of Renner–Teller interaction in both the degenerate electronic states: this interaction is extremely large in the X2Πg state. The principal constants (in cm−1) of the observed states of CNC are as follows:[Formula: see text]The C—N bond length in the ground state of CNC is found to be 1.245 Å.CNC is isomeric with CCN, whose spectrum has been reported previously; some interesting comparisons are made between the spectra of these two molecules.