Measurements of Thermal Rate Constants for the Reactions of N(2D,2P) with C2H4 and C2D4 between 225 and 292 K

The thermal rate constants for the reactions of electronically excited nitrogen atoms, N( 2 D) and N( 2 P), with C 2 H 4 and C 2 D 4 have been measured by using a pulse radiolysis−atomic absorption method between 225 and 292 K. From the results of the kinetic isotope effect for the N( 2 D) reaction, a main reaction mechanism was assigned to be the N addition to the double bond. This conclusion is in accordance with the prediction of our previous ab initio calculations. Variational transition-state theory calculations were performed for the N( 2 D) reaction by using the results of ab initio molecular orbital calculations. It was suggested that correction of the “multiple surface coefficient” is necessary to interpret the measured rate constants. The ratio of the rate constant of N( 2 D) to that of N( 2 P) was found to be close to unity and was much smaller than those for the reactions with H 2 and CH 4 . The deactivation process of N( 2 P) was determined to be the spin-allowed quenching process, N( 2 P) + C 2 H 4 (S 0 ) → N( 4 S) + C 2 H 4 (T 1 ).