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 3P0J and 1D levels very efficiently. Under optimum conditions (different for the two states), up to 85% of the atoms can be converted to the 3P0J 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.