Rate coefficients for quenchingkQand intersystem conversionkTof excited BaO formed in the reaction Ba+N2O(1)rarr;BaO+N2have been measured for several collision partners. Methods are developed and applied here for obtaining quenching rate coefficients in chemiluminescent reactions involving a reservoir state. Experiments were performed between 450 and 1000 K at 1ndash;120 Torr in a modified highhyphen;temperature fasthyphen;flow reactor (HTFFR). The rate coefficients (or their upper limits) are, in ml moleculeminus;1thinsp;sminus;1units:kArQ(600ndash;1000 K) quest;3times;10minus;13;kHeQ(460 K) 3times;10minus;13;kN2Q(600 K) = (4.8plusmn;2.0) times;10minus;12;kN2OQ(600 K) = (4.2plusmn;1.0) times;10minus;10; 2.5times;10minus;10quest;kO2Q(600 K) quest;7.0times;10minus;10;kArT(600 K) quest;1.5times;10minus;11. Incidental data at quest;1000 K indicate thatk1quest;5times;10minus;11, and that the Ba/O2reaction has about the same rate coefficient. In addition to BaO emission, strong Ba atomic emission arising from energy transfer processes was observed for lsqb;Barsqb;gsim;1times;1013mlminus;1atTquest;1000 K. Measurements of the spectral distributions of the Ba/N2O chemiluminescence as a function of lsqb;Arrsqb;, lsqb;Hersqb;, and lsqb;N2rsqb; yield relations among vibrational relaxation rate coefficients:kv,kT, andkQfor specific BaO(Athinsp;1Sgr;) vibrational levels. The set of reactions currently in use to describe the Ba/N2O chemiluminescence is shown to be inadequate to account for the observed changes in BaO(Athinsp;1Sgr;minus;Xthinsp;1Sgr;) spectral distribution with pressure.
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