Heat-pipe-oven reactor studies. III. Chemiluminescence from ternary flame systems

Abstract

We present a summary of results obtained in a quantitative study of the chemiluminescence from several ternary flame systems (volatile polyhalide, alkali metal, and oxidizer) carried out in a heat-pipe-oven reactor (HPOR). The polyhalides studied were: CCl4, GeCl4, SiCl4, SnCl4, PCl3, BCl3, BI3, AsCl3, SCl2, and NF3. Sodium vapor was mostly used for the reduction, and N2O for the oxidation. The emission characteristics of these ternary flames can be classified in three groups: (1) Flames that produced emission from electronically-excited diatomic species. We observed radiation from upper electronic states of SnO, PO, BO, NO, and probably GeO, as well as from CN and C2. These flames also produced radiation from excited alkali atoms; (2) flames that produced strong emission from the various electronic levels of the alkali atoms up to the ionization limit, but no radiation from oxides. This group included SCl2, NF3, and CCl4, reacting with alkali vapors in the presence of N2O; (3) weak flames that produced emission only from the lowest resonance level of Na. This group included SiCl4, AsCl3, and BI3. The photon yields in the first group were on the order of 10−2 to 10−4; in the second group, up to 3%; and in the third group, less than 10−6. The photon yields were strongly pressure-dependent, with the highest yields obtained at the lowest pressure (∼50 mtorr in most cases), which suggests very large quenching cross sections. Possible excitation mechanisms for the atomic and molecular emissions are discussed.