Diode Laser Study of the Product Branching Ratio of the NH₂(X ²B₁) + NO₂ Reaction

Abstract

The reaction of NH2(X 2B1) with NO2 was studied at room temperature using time-resolved infrared diode laser spectroscopy to detect N2O, H2O, and NO products. The N2O + H2O product channel was found to have a branching ratio of 0.14 ± 0.02. Large amounts of NO were detected, but secondary sources of this species prevent a quantitative determination of the branching ratio into the H2NO + NO channel. These results are in contrast to previously published branching ratio data.

Mass-spectrometric determination of product branching probabilities for the NH2 + NO2 reaction at temperatures between 300 and 990 K

“…2 cm3 mole-' s-I at low temperatures, for which they did not have experimentally-determined kinetic data. Our result, together with that of Hershberger [32], also rules out the conclusion of Hack et al [12] that a should be at least 0.95 according to their brief mass spectrometric study. Figure 2 shows the sensitivities of the NH, decay and the N,O and H,Oproduction rates to various processes which occurred in the laser-initiated NH, + NO, + He system at 640 K. The experimental conditions used in the modeling are given in Table I.…”

“…Both total rate constants gave very close room-temperature values, a = 0.19 5 0.02, which is in reasonable agreement with the result of Quandt and Hershberger, a = 0.14 ? 0.03 obtained by diode laser absorption spectroscopy [32] as shown in Figure 1. At higher temperatures, the value of a, derived from the use of the k, recommended by Atkinson et al [17], becomes larger and approaches a = 0.25 at 1000 K; the increase results directly from the de- creasing total rate which requires a larger a to account for the observed N,O yield.…”

The role of NNH in NO formation and control

“…For this reaction we select the overall rate constant from the work of Song et al [98], together with a branching fraction β = k 17 / (k 17 + k 18 ) of 20% [98][99][100][101]. While the value of β is maintained from previous modeling work [22], it is worth noting that the overall rate constant of Song et al is about a factor of two larger.…”

Kinetics of HCCl + NOx reactions

“…For product molecule detection, infrared absorption spectroscopy was used as described in previous publications [9,10]. A tunable lead-salt diode laser provided the infrared probe radiation.…”