Disentangling the Complex Vibrational Spectrum of the Protonated Water Trimer, H⁺(H₂O)₃, with Two-Color IR-IR Photodissociation of the Bare Ion and Anharmonic VSCF/VCI Theory

Abstract

Vibrational spectroscopy of the protonated water trimer provides a stringent constraint on the details of the potential energy surface (PES) and vibrational dynamics governing excess proton motion far from equilibrium. Here we report the linear spectrum of the cold, bare H(HO) ion using a two-color, IR-IR photofragmentation technique and follow the evolution of the bands with increasing ion trap temperature. The key low-energy features are insensitive to both D tagging and internal energy. The D-tagged D(DO) spectrum is reported for the first time, and the isotope dependence of the band pattern is surprisingly complex. These spectra are reproduced by large-scale vibrational configuration interaction calculations based on a new full-dimensional PES, which treat the anharmonic effects arising from large amplitude motion. The results indicate such extensive mode mixing in both isotopologues that one should be cautious about assigning even the strongest features to particular motions, especially for the absorptions that occur close to the intramolecular bending mode of the water molecule.

PyVisA: Visualization and Analysis of path sampling trajectories

“…It should be noted that our work does not aim to improve the current physical understanding of the reaction but instead has chiefly a modeling integration objective. Our results integrates the findings of the work of Geissler et al 22 For an improved physical description of the proton transfer mechanisms, path sampling shall be used with more recent models such as improved SD, 23 density functional theory, 24 Møller‐Plesset perturbation theory, 25 vibrational motion 26,27 and finally, the Neural Network Potentials at Coupled Cluster Accuracy 28 …”

“…This has been claimed to generate large deviations in the rate computation when considering reduced dimensionality approaches 46 . This vibration can be mapped, as an independent degree of freedom, in the initial and final stable states, as well as during the reaction since it can induce a Fermi resonance 26,27 that might significantly alter the reaction dynamic. To assert if the hydrogen distances correlate with the reaction, classifiers can be employed.…”

Unique Structures and Vibrational Spectra of Protic Ionic Liquids Confined in TiO2 Slits: The Role of Interfacial Hydrogen Bonds

“…In addition, the confined cations have a shoulder before the conventional asymmetric N–H stretching vibrational peak at 3344 cm –1 . Above vibrational spectra are different from those of other interfaces such as EAN–air, EAN–carbon nanotube, and water–Au nanoparticle. ,− Some previous works , have confirmed that the characteristic asymmetric stretching vibration peak of N–H at 3344 cm –1 is due to HBs between EAN ion pairs. For the EAN IL molecules confined inside the TiO 2 slits, the EA + cations can form two types of HBs: one with the TiO 2 wall and the other with the NO 3 – anions.…”

Coupled Local-Mode Approach for the Calculation of Vibrational Spectra: Application to Protonated Water Clusters

“…27 Other values of n reveal structures in between the limiting Eigen and Zundel configurations. 26,28 Spectroscopic insights that inform our understanding of the hydrated proton have resulted from a bottom-up approach of investigating PWCs of increasing size. Because the clusters are cold, the IR spectra contain relatively sharp features that are amenable to interpretation in terms of specific configurations and vibrational modes, in contrast to the mostly featureless continuum of the fully hydrated proton in aqueous solution.…”