THE SPECTRUM OF THE FREE NCN RADICAL
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Date
1964
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Ohio State University
Abstract
Several years ago in the flash photolysis of diazomethane a complicated group of bands was found in absorption near 3285 {\AA}$^{1}$. The same system has also been observed in emission when various hydrocarbons are introduced into a stream of active $nitrogen^{2}$. Experiments with deuterated diazomethane and $C^{12}$ substituted diazomethane showed that the molecule responsible for the spectrum did not contain any hydrogen but did contain one and only one carbon atom. While on the basis of these old experiments it appeared very probable that the carrier of the spectrum is the free NCN radical, a final proof has been obtained only recently when on the basis of improved spectrograms obtained by using a mixture of dicyanogen and diazomethane a fairly complete analysis of the main band became possible. The rotational analysis shows that the molecule is linear and symmetric in both the upper and lower state and that the transition is $^{3}II_{u}-^{3}\Sigma^{-}_{g}$. The triplet splittings in both states have been accurately evaluated, the C---N distance in the ground state is 1.232 {\AA}. Apart from the 0-0 band only the 1-1 band in the bending vibration appears in absorption. This band shows clearly the effects of Renner-Teller interaction, the splitting parameter being $\epsilon \omega_{2} \approx 85 cm^{-1}$. None of the vibrational frequencies could be determined.
Description
$^{1}$ G. Herzberg. Proc. Roy. Soc. 262A, 291 (1961). G. Herzberg. ICSU Review 4, 179 (1962). G. Herzberg and P. A. Warsop. Can. J. Phys. 41, 286 (1963). $^{2}$ K. R. Jennings and J. R. Linnett. Trans. Far. Soc. 46, 1737 (1960).
Author Institution: Division of Pure Physics, National Research Council
Author Institution: Division of Pure Physics, National Research Council