The cis and trans structures of the NO dimer cation

The NO dimer cation, (NO)(2)(+), has been studied using high-level ab initi o calculations. The ground state is determined to be the trans isomer, whic h has C-2h symmetry. The cis, C-2v, isomer lies ca. 100 cm(-1) above this, as calculated at the RCCsD(T)/aug-cc-pVQZ(no g)//UQCISD/6-311 + G(3df) leve l of theory. The equilibrium geometry of the trans isomer has an N-N bond l ength of 2.25 Angstrom and a NNO bond angle of 112 degrees. A reassignment of the ZEKE spectrum of the NO dimer is postulated on the basis of calculat ed harmonic vibrational frequencies. (C) 1999 Elsevier Science B.V. All rig hts reserved.