Knowledge Bank

Results of studies on the pressure-dependent chemiluminescence and photon yields from metal-rich Sr(g) + $N2O$ or $N2O/CO$ (1:1) flames burning at 45-250 mtorr will be presented. The $Sr/N2O$ reaction yields a many-line spectrum at low pressures (45 mtorr), probably from rotationally-hot SrO, $A1\Sigma$ and $A^\{\backslash prime\backslash prime\}^\{1\}\backslash Pi$. At pressure $>90$ mtorr, the $Sr/N2O$ and $Sr/N2O/CO$ reactions yield emission from $A^\{1\}\backslash Sigma,\; A^\{\backslash prime\backslash prime\}^\{1\}\backslash Pi$, and $B1\Pi$ states to the Sro ground state, $X1\Sigma$. This represents the first observation of B-X emission in a chemiluminescent strontium atom oxidation diffusion flame. Addition of CO increases the photon yield of the $Sr/N2O$ flame and also generates the ``arc-bands’’ of Sro. Although the lack of spectral information on excited states of SrO prohibits identification of primary and secondary reaction channels and products, the qualitative behavior of the results suggests that metastable $Sr(3p)$ atoms are important $Sr/N2O/CO$ flames, but not in $Sr/N2O$ flames. These results will be incorporated into a general discussion of alkaline earth metal + $N2O$ or $N2O/CO$ chemiluminescence mechanisms.