Radiation from the reactions of NO+ with Cl− and I−

A study of the ion-ion recombination reactions of NO+ with Cl− and I− has been carried out using our flowing afterglow/Langmuir probe (FALP) apparatus at 300 K. These recombination reactions proceed by the transfer of an electron from the I− and Cl− ions to the NO+ ions producing neutral, electronically excited NO molecules and ground state halogen atoms. For ground state reactant ions, only the two lowest electronic states of NO, i.e. the A2Σ+ and the B2Πr states can be generated. This FALP study shows that only NO γ-bands are emitted by the thermalised NO+/Cl− plasma whereas both NO γ-bands and NO β-bands are emitted by the thermalised NO+/I− plasma. From these observations together with our measured values of the recombination coefficients for the reactions, and from a consideration of the reaction energetics, we conclude that electron transfer from both Cl− and I− to NO+ most probably occurs at short distances on the repulsive potential wall and not at longer distances as is usually assumed for this type of reaction.