CHEMILUMINESCENCE FROM THE $Ca(^{1}D) + O_{2}$ AND $Ca(^{3}P^{O}) + N_{2}O$ REACTIONS: ABSOLUTE CROSS SECTIONS, PHOTON YIELDS, AND Ca0 DISSOCIATION ENERGY
Loading...
Date
1980
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The chemiluminescent reactions $Ca(^{1}D) + O_{2} \rightarrow CaO^{*} + O$ (1) and $Ca (^{3}p_{\tau} ^{O}) + N_{2}O \rightarrow CaO^{*} + N_{2}$ (2) have been studied under single-collision conditions with a beam-gas scattering apparatus. Chemiluminescence was observed over 675-900 nm and 360-900 nm, respectively. In reaction (1), absolute cross sections for production of the emitting $CaO(A^{\prime}\ ^{1}\pi)$ and $CaO(A ^{1}\Sigma^{+})$ states were found to be $(3.2 \pm 1.4) \times 10^{-16}$ $cm^{2}$ and $(1.0 \pm 0.48) \times 10^{-16}$ $cm^{2}$, respectively, and a lower bound of $(5.2 \pm 2.5)%$ was derived for the total photon yield. By identification of the highest $CaO^{*}$ level formed, the CaO dissociation energy was determined to be $4.11 \pm 0.07$ eV. This value is in agreement with the $JANAF^{1}$ recommended value of $3.95 \pm 0.22$ eV but is significantly lower than recent chemiluminescence $result^{2}$ of $4.76 \pm 0.15$ eV. In the more energetic reaction (2), the total photon yield was 10--20%, but the identification of the emitting CaO states was hampered by the lack of sharp band heads and insufficient spectroscopic information. Evidence will be presented for a collisional population at $N_{2} O$ pressures above $10^{-3}$ Torr of emitting $CaO^{*}$ states from ""dark"" states directly produced in reaction (2). A similar process in analogous $Ba(^{1}S)$ oxidation reactions has received much attention.
Description
$^{1}$M. W. Chase, JR., J. L. Curnutt, R. A. McDonald, and A. N. Syverud, J. Phys. Chem. Ref. Data 7, 793 (1978). $^{2}$F. Engelke, R. K. Sander, and R. N. Zare, J. Chem. Phys. 65, 1146 (1976).
Author Institution:
Author Institution: