New combination bands of N₂O-CO₂, N₂O-OCS, and N₂O-N₂ complexes in the N₂O ν₁ region Available to Purchase

Spectra of the weakly bound complexes N₂O-CO₂, N₂O-OCS, and N₂O-N₂ were studied in the region of the ν₁ fundamental of N₂O (∼2224 cm⁻¹) using a tunable quantum cascade laser to probe a pulsed supersonic jet expansion with an effective rotational temperature of about 2.5 K. One new combination band was observed for each complex: a band involving an intermolecular in-plane bending mode for N₂O-N₂, a band involving the disrotation (in-plane geared bend) for of N₂O-CO₂, and a band involving the out-of-plane torsional vibration for isomer b of N₂O-OCS. Small perturbations were noted for the N₂O-OCS band. Because of the absence of theoretical prediction, the nature of the intermolecular bending mode for N₂O-N₂ has not been identified. The resulting intermolecular frequencies are 34.175(1), 17.107(1), and 22.334(1) cm⁻¹ for N₂O-CO₂, N₂O-OCS, and N₂O-N₂, respectively. In addition, the previously known fundamental band of N₂O-N₂ at 2225.99 cm⁻¹ was analyzed in improved detail. This band exhibits very weak a-type transitions which were not detected in the first infrared observation of this complex, indicating that N₂O-N₂ is not exactly T-shaped. That is, the N₂O molecular axis is not exactly perpendicular to the a-inertial axis, in agreement with a previous structural determination of this complex by rotational spectroscopy.