Spectroscopic and theoretical characterization of linear centrosymmetric N≡N⋅⋅H+⋅⋅N≡N

Abstract

The first high resolution infrared spectrum of the ionic complex N2⋅⋅H+⋅⋅N2 and its deuterated derivative is reported. The spectra were obtained in direct absorption in a supersonic slit nozzle plasma. The observed rovibrational transitions were assigned to the ν3 antisymmetric NN stretching vibration and the spectrum is consistent with a linear centrosymmetric equilibrium structure. The band origin is found at 2352.2364(6) cm−1 and the ground state rotational constant is determined as B″=0.081 809(14) cm−1. The assignment is supported by ab initio calculations including electron correlation effects. The best estimate for the equilibrium structure is Re (NN)=1.095 Å and re (N⋅⋅H)=1.277 Å. The transition moment of the ν3 band of N2⋅⋅H+⋅⋅N2 is predicted to be 0.21 D, an order of magnitude larger than for the NN stretching vibration of HN2+. The equilibrium dissociation energy De for fragmentation into N2 and HN2+ is calculated to be ∼5900 cm−1.