The gas-phase structure of the asymmetric, trans-dinitrogen tetroxide (NO), formed by dimerization of nitrogen dioxide (NO), from rotational spectroscopy and ab initio quantum chemistry.

We report the first experimental gas-phase observation of an asymmetric, trans-NO formed by the dimerization of NO. In additional to the dominant NO species, rotational transitions have been observed for all species with single N and O substitutions as well as several multiply substituted isotopologues. These transitions were used to determine a complete substitution structure as well as an r structure from the fitted zero-point averaged rotational constants. The determined structure is found to be that of an ON-O-NO linkage with the shared oxygen atom closer to the NO than the NO (1.42 vs 1.61 Å). The structure is found to be nearly planar with a trans O-N-O-N linkage. From the spectra of the NNO species, we were able to determine the nuclear quadrupole coupling constants for each specific nitrogen atom. The equilibrium structure determined by ab initio quantum chemistry calculations is in excellent agreement with the experimentally determined structure. No spectral evidence of the predicted asymmetric, cis-NO was found in the spectra.