Linear and centrosymmetric N2⋯Ar+⋯N2

Abstract

A high resolution infrared absorption spectrum of the ionic complex N2⋯Ar+⋯N2 has been observed by tunable diode laser spectroscopy through a supersonic planar plasma. Seventy-six rovibrational transitions were measured involving excitation of the antisymmetric NN (ν3) stretching fundamental. The band origin is at 2288.7272(2) cm−1 and the ground state rotational constant is determined as B0=0.034 296(7) cm−1. The spectrum shows a clear spin-statistical intensity alternation and is consistent with a linear and centrosymmetric equilibrium geometry and a ground state with Σu+2 symmetry. The charge is predominantly located on the argon atom. The assignment is supported by high level ab initio calculations carried out. The best estimate for the equilibrium geometry is Re(NN)=1.1014 Å and re(Ar⋯N)=2.3602 Å, yielding Be=0.034 297 cm−1. The equilibrium dissociation energy De for fragmentation into N2 and [ArN2]+ is calculated to be ∼1.7 eV.