Crossed-beam chemiluminescent studies of alkaline earth atoms with ClO2

Abstract

Chemiluminescence resulting from the reaction M+ClO2, M=Mg, Ca, Sr, or Ba, has been observed in crossed molecular beams. Two special features are found: (1) selective formation of MO* in the A′ 1Π state in preference to the isoenergetic A 1Σ+ state; and (2) the formation of MCl* in various electronic states. Although the MCl* product results from attack of the central Cl atom in ClO2, its cross section is comparable to that of MO*. The cross section for chemiluminescence is a small fraction of the total reaction cross section, which is larger than gas kinetic. From the chemiluminescent spectra the relative electronic, vibrational, and rotational population distributions are derived and the following lower bounds are placed on the MO dissociation energies: D00(CaO) ?109.7±3.5 kcal/mole; D00(SrO) ?107.7±3.5 kcal/mole; and D00(BaO) ?133.6±3.5 kcal/mole. The reaction dynamics are discussed in terms of an electron transfer from M to the half-filled antibonding orbital of ClO2.