Collisional dynamics of the BrCl B 3Π(O + ) state. I. Electronic quenching

Electronic quenching of BrCl B ³Π(O⁺) was studied in pulsed and steady-state laser induced fluorescence experiments. BrCl(B) deactivation rate coefficients were determined as a function of vibrational quantum number for the following collision partners: He, Ne, Ar, Kr, N₂, O₂, and Cl₂. Quenching from a vibrationally thermalized, 300 K BrCl(B,v') distribution by the noble gases N₂, and Cl₂ was slow with all rate coefficients less than 4.3±0.7×10^-13 cm³ molecule^-1 s^-1 . The quenching by O₂ was much faster with a rate coefficient of 6.5±0.6×10^-12 cm³ molecule^-1 s^-1 . The quenching of BrCl(B), under single collision conditions, depends strongly on vibrational quantum number of BrCl(B), with rate coefficients ranging from 4.3±0.1×10^-13 cm³ molecule^-1 s^-1 for v'=0 to 1.4±0.3×10^-10 cm³ molecule^-1 s ^-1 for v'=6 under collisions with Cl₂ and with rate coefficients ranging from 1.5±0.3×10^-13 cm³ molecule^-1 s^-1 for v'=0 to 1.0± 0.4×10^-10 cm³ molecule^-1 s^-1 for v'=6 under collisions with He. Several mechanisms for the electronic deactivation of BrCl(B) are discussed. The radiative lifetime of BrCl(B) was determined to be 38.7±1.7 μs, independent of vibrational level for v'≤6.