ESR Intensity Relations and Some Gas-Phase Chemical Kinetics of the OD Radical

Abstract

The theoretical intensity relations for the quantitative determination of gas‐phase OD radical and D atom concentrations by ESR spectroscopy are derived. OD was generated by the fast reaction of D atoms with NO₂, and chemical kinetic rate constants for the reactions $$\mathrm{OD}+\mathrm{OD}\to {\mathrm{D}}_2\mathrm{O}+\mathrm{O},$$ $$\mathrm{OD}+\mathrm{CO}\to {\mathrm{CO}}_2+\mathrm{D},$$ were measured at 300°K by following the OD decay in a fast flow system. The values obtained were k₂=0.95±0.10×10¹² and k₄=3.30±0.10×10¹⁰ in cubic centimeters mole⁻¹·second⁻¹. Rate constants for the corresponding OH reactions previously measured in this laboratory by the same technique give ratios k_H/k_D of 1.6 for Reaction [2] and 3.5 for Reaction [4]. These ratios are discussed in terms of the absolute reaction rate theory of isotopic species. It is shown that reasonable assumptions about the activated complexes lead to good agreement with experiment.