Nonpolar nitrous oxide dimer: Observation of combination bands of (14N2O)2 and (15N2O)2 involving the torsion and antigeared bending modes

Spectra of the nonpolar nitrous oxide dimer in the region of the N2O nu(1) fundamental band were observed in a supersonic slit-jet apparatus. The expansion gas was probed using radiation from a quantum cascade or a tunable diode laser, with both lasers employed in a rapid-scan signal averaging mode. Four bands were observed and analyzed: new combination bands involving the intermolecular conrotation of the monomers (A(g) antigeared bend) for ((N2O)-N-14)(2) and ((N2O)-N-15)(2), the previously reported torsional combination band for ((N2O)-N-14)(2) with improved signal-to-noise ratio, and the same torsional combination band for ((N2O)-N-15)(2). The resulting frequencies for the intermolecular antigeared mode are 96.0926(1) and 95.4912(1) cm(-1) for ((N2O)-N-14)(2) and ((N2O)-N-15)(2), respectively. This is the third of the four intermolecular frequencies which has now been measured experimentally, the others being the out-of-plane torsion and the geared bend modes. Our experimental results are in good agreement with two recent high level ab initio theoretical calculations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3697869]