Knowledge Bank

Recently, we have reported the first gas-phase infrared spectrum of an alkaline earth metal oxide, $CaO1$. Substantial improvement has been made by multipassing the infrared radiation through the low pressure flame in which the oxides are formed. More than 40 rovibrational transitions of the fundamental band and the first and second hot band have been measured. By comparing the relative intensities of nearby fundamental and hot band transitions, the state distribution of CaO in the flames has been monitored. Depending on the flame conditions, the vibrational temperature varied between 500 and 1500 K, whereas the rotational temperature was always close to 350 K. New results for barium oxide include spectra for a number of hot bands of $\mathrm{<mrow\; data-mjx-texclass="ORD">138</mrow>}BaO,137BaO,136BaO,135BaO$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">134</mrow>}BaO.$ Using the isotopic dependence of the constants, a set of Dunham-coefficients was obtained from these data.