THE ELECTRONIC SPECTRUM OF THE NCO RADICAL

Author Institution: Division of Pure Physics, National Research Councel“A new spectrum has been photographed in the 2nd, 3rd and 4th orders of a 21-foot grating spectrograph during the flash photolysis of ethyl isocyanate and isocyanic acid, using an absorption path of 10 meters. The absorption consists of one series of violet shaded bands in the region $3600-4490 \AA$ and three weak band heads between 2850 and 3040 $\AA$. The rotational and vibrational structures of the longer wavelength band system seem to indicate that it arises from a $^{2}\Sigma-^{2}\Pi$ transition of a linear triatomic molecule. The appearance of these bands, together with previous work of D. W. G. Style, has served to assign the bands to the NCO molecule. A strong band at 4404 $\AA$ has been identified as the $00^{\circ}0-00^{\circ}$0 band. In addition to absorption from the lowest vibrational level of the ground state, bands involving one quantum of the ground state bending vibration have been observed. The structure of these bands indicates that there is a large coupling, or the type described by Renner, between the vibrational and electronic singular momentum. The results of a vibrational and rotational analysis of the bands, which is now in progress, will be presented.