Reactions of N + (3P) ions with normal, para, and deuterated hydrogens at low temperatures

The reactions of N⁺(³P) ions with normal, para, and deuterated hydrogens have been examined at temperatures below 163 K by using the CRESU technique with both helium and nitrogen buffer gases. All these reactions have decreasing rate coefficients with decreasing temperature. Comparison of the data for normal and para-H₂ reveals the drastic importance of rotational energy in promoting these processes. Analysis of these results shows a better agreement between the n-H₂, p-H₂, and HD data if the spin-orbit energy of N⁺(³P) is also considered as efficient as kinetic and rotational energies in driving the reactions. It follows that the endothermicity of the reaction N⁺(³P₀) +H₂(X ¹Σ⁺_g,J=0) →NH⁺(X ²Π,J=0) +H(²S) is (18±2) meV. This yields a proton affinity of N equal to (3.524±0.003) eV and a dissociation energy of NH of (3.42±0.01) eV.