Flame-Photometric Determination of the Dissociation Energies of the Alkaline-Earth Oxides

Two independent methods for determining dissociation energies of CaO, SrO, and BaO from optical measurements of band and line intensities in CO—air flames are described. The emitter of the measured bands has been shown not to be hydroxide molecules or molecules containing more than one metal atom. From a comparison of the results for both methods it can be concluded that the value of the electronic partition function of the alkaline-earth oxide molecule is around 6. Recommended values for the dissociation energies are (in electron volts): 3.96±0.06, 4.11±0.06, and 5.00±0.10 for CaO, SrO, and BaO, respectively. A comparison with the literature data is given.