Spectroscopic and theoretical characterization of linear centrosymmetric N N center dot center dot H+center dot center dot N N

The first high resolution infrared spectrum of the ionic complex N-2.. H+.. N-2 and its deuterated derivative is reported. The spectra were obtained i n direct absorption in a supersonic slit nozzle plasma. The observed rovibr ational transitions were assigned to the nu(3) antisymmetric NN stretching vibration and the spectrum is consistent with a linear centrosymmetric equi librium 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 co rrelation effects. The best estimate for the equilibrium structure is R-e ( NN) = 1.095 Angstrom and re (N .. H) = 1.277 Angstrom. The transition momen t of the nu(3) band of N-2.. H+.. N-2 is predicted to be 0.21 D, an order o f magnitude larger than for the NN stretching vibration of HN2+. The equili brium dissociation energy D-e for fragmentation into N-2 and HN2+ is calcul ated to be similar to 5900 cm(-1). (C) 1999 American Institute of Physics. [S0021-9606(99)01342-2].