CHEMILUMINESCENCE IN REACTIONS OF N+ IONS WITH HYDROGEN AND HYDROCARBONS .1. ROTATIONAL-VIBRATIONAL PRODUCT EXCITATION

Chemiluminescent ion-molecule atom-exchange reactions between N+ ions and H2, CH4, C2H4, C 2H6, and C3H8 were studied in a beam-gas arrangement. The collision energy ranged between 1.6 and 150 eV c.m.. The observed product was in all cases NH (A 3Π) radiating into the NH ground state. All reactions proceed nonadiabatically. The NH (A→X) emission spectra obtained were simulated on a computer. This yielded detailed rotational population distributions for both the v′ = 0 and v′ = 1 vibrational levels of NH(A), as well as the (v′ = 1)/(v′ = 0) vibrational population ratio. At high collision energy the distributions are affected by predissociation, but below 5 eVc.m. in the case of CH4 the observed rotational distribution is that resulting directly from the reactive collision. In this case the dependence of the mean rotational energy on the collision energy strongly suggests a stripping mechanism for the reaction, while the reactions with the heavier hydrocarbons clearly do not proceed by stripping. © 1979 American Institute of Physics.