MEASUREMENTS OF THE BRANCHING RATIOS FOR THE REACTION OF O(1D2) WITH N2O

The relative rate constants for the reaction channels O(1D 2) + N2O → {N2 + O2 (1a) 2NO (1b) N + NO2 (1c) O(3P) + N2O (1d) 2O( 3P) + N2 (1e) were determined using chemical-ionization mass spectrometry to measure the products of Reaction (1). O(1D 2) atoms were produced by the photodissociation of N2O at wavelengths greater than 1950 Å. The measurements were carried out in mixtures of N2O with helium added to remove the excess kinetic energy carried by the O(1D2). We find the ratio k 1a/k1b is sensitive to the presence of helium increasing from a value of 0.68 in pure N2O to a value of 0.80 with [He]/[N 2O]≥10. In addition, at 300 K we find that (1a) and (1b) constitute the only significant channels for the reaction with (k1c + k1d + k1e)/(k1a + k1b)≤0.038. The ratio k1a/k1b is found to decrease slowly with increasing temperature over the range 170-434 K. These data can be fitted by the expression k1a/k1b = (0.72±0.11) + (21.6±7.0)/T. © 1979 American Institute of Physics.