Carbon and hydrogen kinetic isotope effects for the reaction of Cl with CH4: Consolidating chemical kinetics and molecular dynamics measurements

摘要

In order to estimate carbon and hydrogen kinetic isotope effects for the reaction Cl+ CH, at atmospheric temperatures, measured values of the rates of Cl reacting with (CH4)-C-13, (CH3D)-C-12, (CH2D2)-C-12, (CHD3)-C-12, and (CD4)-C-12 relative to those of Cl+(CH4)-C-12 were fit using a model that accounts for quantum mechanical tunneling. The model also includes vibrational enhancement of the reaction rate by excitation of the bending and stretching modes of CH,. These fits allow extrapolation of measured values to temperatures outside the range in which they were measured. In addition, the kinetic isotope effect for Cl+(CH4)-C-14 was predicted using this model based on the results for Cl+ (CH4)-C-13. The model results for Cl+(CH4)-C-14, Cl+(CH4)-C-13, and Cl+(CH3D)-C-12 were parameterized for use in atmospheric models. [References: 50]