Knowledge Bank

A gas flow tube reactor has been used to generate a chemiluminescent flame from the reactions $Pb+N2OandPb+O2$. The throughput of lend vapor from the furnace to the reactions region has been increased, resulting in more intense flames. Emission was observed in the region 200-800 nm from five different electronic states. They were the a, b, A, B, and D states. Emission from the a state was generally the most intense, while that from the forbidden b state was weakest. The assignments compare well with published work and in addition previously unreported bands assignable to emissions from the b state were observed. Spectra obtained with the two different oxidizers were compared. Significant differences in spectral line intensities were recorded. The dependence of the chemiluminescent emission spectrum of PbO on changes in oxidizer pressure was studied at various oxidizer pressures below 1.0 Torr. Significant enhancement of emission from the higher energy B and A states was noted in the $Pb+O2$ reaction at 0.4 Torr of $O2$. This low pressure enhancement mechanism has not been reported previously. The $Pb+O2$ reaction would probably be the most likely to exhibit a population inversion since the higher lying states are more heavily populated. It is unlikely however that an inversion could be achieved without the introduction of some other excited species into the flame to serve as an energy transfer means.