Intermolecular vibrational states far above the van der Waals minimum: Combination bands of the polar N2O dimer

Infrared combination bands of the polar isomer N2O dimer are observed for first time, using a tunable infrared laser source to probe pulsed slit-jet supersonic expansion in nu1 region (~2240 cm-1). One band involves torsional (out-of-plane) intermolecular mode and yields frequency 19.83 cm-1 if associated with out-of-phase fundamental (N2O nu1) vibration monomers dimer. The other band, which is highly perturbed, an in-plane geared bend 22.74 cm-1. results compared high level ab initio calculations. less likely alternate assignment in-phase would give frequencies 17.25 20.16 cm-1, respectively.