Abstract-Deconstructing Prominent Bands in the Terahertz Spectra of H7O3+ and H9O4+: Intermolecular Modes in Eigen Clusters

Tim K Esser, Harald Knorke, Knut R. Asmis, Wieland Schöllkopf, Qi Yu, Chen Qu, Joel M Bowman, Martina Kaledin,

http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.7b03395

We report experimental vibrational action spectra (210-2200 cm-1) and calculated IR spectra, using recent ab initio potential energy and dipole moment surfaces, of H7O3+ and H9O4+. We focus on prominent far-IR bands, which post-harmonic analyses show, arise from two types of intermolecular motions, i.e., hydrogen bond stretching and terminal water wagging modes, that are similar in both clusters. The good agreement between experiment and theory further validates the accuracy of the potential and dipole moment surfaces, which was used in a recent theoretical study that concluded that infrared photodissociation spectra of the cold clusters correspond to the Eigen isomer. The comparison between theory and experiment adds further confirmation of the need of post-harmonic analysis for these clusters.