# The Carbon Monoxide Flame Bands

R. N. Dixon

## Abstract

The carbon monoxide flame bands have been photographed under high resolution from an afterglow source. Bands in the wavelength range 3100 to 3800 $\overset{\circ}{\mathrm A}$ show a pattern which has been reproduced by calculations of the energies of high vibrational levels of the $^1\sum^+_g$ ground state of CO$_2$. The structure of this energy level pattern is strongly affected by extensive Fermi resonance in the $^1\sum^+_g$ state. The spectrum is emitted by excited CO$_2$ molecules which radiate to the ground state from the lowest vibrational level and from the $v'_z$ = 1 level of a B$_2$ state. This excited state lies approximately 46 000 cm$^{-1}$ above the lowest level of the ground state, and has an OCO angle of 122 $\pm$ 2$^\circ$ and a CO bond length of 1.246 $\pm$ 0.008 $\overset{\circ}{\mathrm A}$. Combination of these results with the work of other authors shows that the excited state is a $^1$B$_2$ state, and that the carbon monoxide flame bands are associated with the weak absorption system of CO$_2$ at 1475 $\overset{\circ}{\mathrm A}$.