A merged molecular beam study of the endoergic associative ionization reaction N(2 D )+O(3 P ) →NO++ e

We have measured the absolute total cross section as a function of kinetic energy for the endoergic association ionization reaction N+O→NO++e−. Analysis of data obtained with various mixtures of N atom electronic states enables us to determine that the dominant mechanism is the reaction of the N(2D) metastable excited state with the O(3P) ground state. The reaction cross section shows an abrupt onset at the expected threshold energy of 0.38 eV, and has a maximum of about 0.6 Å2 at 10.5 eV. The data in the threshold region yield thermal rate coefficients larger than those estimated previously by Lin and Teare. A theoretical interpretation of these data is given by S. E. Nielsen and J. S. Dahler in a companion paper immediately following this one.