Stories that are encoded in vibrational spectra: Obtaining insights into the spectroscopy of water from studies of ion-water complexes

In this talk, I will discuss recent work in our group in which we made connections between proton transfer processes and hydrogen bonding and vibrational frequencies and intensities.  Due to the large amplitude motions associated with proton transfer along a hydrogen bond, the vibrational spectra of these systems contain features that cannot be understood by the usual harmonic description of molecular vibrations, and even the widths of anticipated features encode information about these anharmonic couplings.  The breakdown of the harmonic treatment of molecular vibrations reflects both the anharmonicity along this coordinate and coupling between this mode and other low frequency modes in these systems.  It also reflects changes in the electronic structure as molecules vibrate. The presentation will draw from reported vibrational spectra for systems either containing intra- or intermolecular hydrogen bonds.  The focus will of the talk will be on the methods used, including harmonic treatments, vibrational perturbation theory in internal coordinates and Diffusion Monte Carlo approaches, and insights gained by studying the spectra of these molecular systems.  Implications of these studies of ion-water complexes to insights into the condensed phase dynamics and spectroscopy will also be discussed.