Letters to the Editor

Abstract

OF the many values which have been suggested for D(CO), the high value of 11·1 eV. and Hagstrum's value of 9·61 eV. seem most likely, as recently pointed out¹. Dr. Howell's discussion of the F¹II-state certainly gives strong support to the latter value. It should be remembered, however, that Birge–Sponer extrapolations for highly excited states may not be reliable, and indeed may be quite anomalous, as for silver hydride. Also it is likely that for the excited states of carbon monoxide there may be potential maxima, and the limit of the extrapolation will then be the maximum instead of the dissociation limit. In the reaction zones of flames much of the light emission is due to chemiluminescence, and it is not easy to account for this unless we are able to postulate reactions which are highly exothermic and which require the high value for D(CO). The 9·61 value would, however, give a more satisfactory comparison with the iso-electronic molecule N₂, for which I favour a dissociation energy of 9·76 eV.