Chemiluminescence from the Ca(4s3d 1D)+O2 reaction: Absolute cross sections, photon yield, and CaO dissociation energy

Abstract

Chemiluminescence has been observed at 675 to 900 nm from the reaction Ca(4s3d 1D)+O2→CaO*+O under single collision conditions. From the short wavelength limit of the chemiluminescence, the dissociation energy of CaO is found to be 4.11±0.07 eV, in agreement with the lower of two currently disputed values. Absolute chemiluminescence cross sections for emission from CaO(A′ 1Π) and CaO(A 1Σ+) are (3.2±1.4)×10−16 cm2 and (1.1±0.48)×10−16 cm2, respectively, and a lower bound of (5.2±2.5) is given for the total photon yield. The present Ca* source, in which a gaseous discharge is used to excite the atoms, was found to produce the metastable 3 P 0 J and 1D levels very efficiently. Under optimum conditions (different for the two states), up to 85% of the atoms can be converted to the 3 P 0 J levels, and 5% into 1D. A previous laser fluorescence study [L. Pasternack and P. J. Dagdigian, Chem. Phys. 33, 1 (1978)] of the reactions of Ca* with O2 and CO2 is reinterpreted using the lower value of the CaO dissociation energy.