Nitrous oxide dimer: Observation of a new polar isomer

Spectra of the nitrous oxide dimer (N2O)(2) are studied in the region of the N2O nu(1) fundamental band around 2230 cm(-1) using a rapid-scan tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. The previously known band of the centrosymmetric nonpolar dimer is analyzed in improved detail, and a new band is observed and assigned to a polar isomer of (N2O)(2). This polar form of the dimer has a slipped parallel structure, rather similar to the slipped antiparallel structure of the nonpolar form but with a slightly larger intermolecular distance. The accurate rotational parameters determined here should enable a microwave observation of the polar N2O dimer. The need for a modern ab initio investigation of the N2O-N2O intermolecular potential energy surface is emphasized. (c) 2007 American Institute of Physics.