HTFFR kinetic studies of the fate of excited BaO formed in the Ba/N2O chemiluminescent reaction

摘要

Rate coefficients for quenchingkQand intersystem conversionkTof excited BaO formed in the reaction Ba+N2O(1)→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 1–120 Torr in a modified high‐temperature fast‐flow reactor (HTFFR). The rate coefficients (or their upper limits) are, in ml molecule−1 s−1units:kArQ(600–1000 K) ?3×10−13;kHeQ(460 K) <3×10−13;kN2Q(600 K) = (4.8±2.0) ×10−12;kN2OQ(600 K) = (4.2±1.0) ×10−10; 2.5×10−10?kO2Q(600 K) ?7.0×10−10;kArT(600 K) ?1.5×10−11. Incidental data at ?1000 K indicate thatk1?5×10−11, 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 Ba≳1×1013ml−1atT?1000 K. Measurements of the spectral distributions of the Ba/N2O chemiluminescence as a function of Ar, He, and N2 yield relations among vibrational relaxation rate coefficients:kv,kT, andkQfor specific BaO(A 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(A 1Sgr;−X 1Sgr;) spectral distribution with pressure.