Photodissociation of CO2 to Produce CO(<i>a</i> 3Π)

Abstract

Carbon dioxide in a helium buffer at room temperature was irradiated with a photon beam of wavelengths 1090 to 850 Å. ``Phosphorescence'' from the CO(a 3Π - X 1Σ) Cameron bands was observed. The phosphorescent yield is zero at threshold and increases smoothly to a maximum of ∼ 60% near 900 Å. The smoothness of the percentage yield was an unexpected observation and is explained by postulating that the relevant potential surface crossings are outside the Franck-Condon region of CO2 absorption. Approximate vibrational distributions have been determined and are also smooth functions of photon energy.