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

TL;DR

This study reports the first observation of infrared combination bands of the polar N2O dimer, revealing intermolecular vibrational states far above the van der Waals minimum, and compares experimental results with ab initio calculations.

Contribution

It presents the first experimental observation of specific intermolecular vibrational combination bands of the N2O dimer and compares these with theoretical calculations.

Findings

Observation of two intermolecular vibrational combination bands.

Determination of torsional and geared bend frequencies.

Comparison with high-level ab initio calculations.

Abstract

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