A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Br(P2(3/2)) + NO2 association reaction as a function of temperature (259-432 K), pressure (12.5-700 Torr), and buffer gas identity (He, Ar, H2, N2, CO2, CF4, SF6). The reaction is found to be in the falloff regime between third and second order over the entire range of conditions investigated. At temperatures below 350 K, the association reaction is found to be irreversible on the time scale of the experiment (approximately 30 ms). At higher temperatures reversible addition is observed, allowing equilibrium constants for BrNO2 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data are in only fair agreement and lead to the following thermochemical parameters for the association reaction: DELTA-H-degrees-298 = -19.6 +/- 1.7 kcal mol-1, DELTA-H-degrees-0 = -18.6 +/- 2.0 kcal mol-1, DELTA-S-degrees-298 = -29.3 +/- 4.2 cal mol-1 K-1; DELTA-H(f)-degrees-298(BrNO2) = 17.0 +/- 1.8 kcal mol-1 (uncertainties are 2-sigma estimates of absolute accuracy). The value for DELTA-H-degrees-0 determined in this study has been employed to calculate k0SC, the low-pressure third-order rate coefficient in the strong collision limit, by using the method of Troe; calculated values of k0SC are inconsistent with experimental results unless DELTA-H-degrees-0 is assigned a value near the lower limit derived from analysis of the high-temperature approach to equilibrium data, i.e., DELTA-H-degrees-0 almost-equal-to -16.6 kcal mol-1. A potential source of systematic error in the calculation of both k0SC and the absolute entropy of BrNO2 results from the complete lack of knowledge of the energies and degeneracies of the electronic states of BrNO2. The procedure developed by Troe and co-workers has been employed to extrapolate experimental falloff curves to the low- and high-pressure limits. Derived values for k0(M,298K) in units of 10(-31) cm6 molecule-2 s-1 range from 2.75 for M = He to 6.54 for M = CO2; 2-sigma uncertainties are estimated to be +/- 20%. Values for k0(N2,T) in units of 10(-31) cm6 molecule- s-1 are 5.73 at 259 K, 4.61 at 298 K, and 3.21 at 346 K; the observed temperature dependence for k0(N2,T) is consistent with the theoretical temperature dependence for beta-ck0SC. Values for k-infinity(T) in units of 10(-11) cm3 molecule-1 s-1 are 2.86 at 259 K, 3.22 at 298 K, and 3.73 at 346 K; 2-sigma uncertainties are estimated to be a factor of 2. Approximate falloff parameters in a convenient format for atmospheric modeling are also derived.
