Observation of the Low-Frequency Spectrum of the Water Dimer as a Sensitive Test of the Water Dimer Potential and Dipole Moment Surfaces

• Type of Material: Article
• Authors: Dr. Raffael Schwan, Ruhr-Universität Bochum; Dr. Chen Qu, Emory University; Dr. Devendra Mani, Ruhr-Universität Bochum; Nitish Pal, Ruhr-Universität Bochum; Dr. Lex van der Meer, Radboud University, Nijmegen; Dr. Britta Redlich, Radboud University, Nijmegen; Prof. Claude Leforestier, Université de Montpellier; Joel Bowman, Emory University; Gerhard Schwaab, Ruhr-Universität Bochum; Prof. Martina Havenith, Ruhr-Universität Bochum
• Language: English
• Date: 2019-08-14
• Publisher: WILEY-V C H VERLAG GMBH
• Publication Version: Final Published Version
• Copyright Statement: © 2019 The Authors.
• License: Creative Commons Attribution-NonCommercial 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1002/anie.201906048
• Title of Journal or Parent Work: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
• Volume: 58
• Issue: 37
• Start Page: 13119
• End Page: 13126
• Grant/Funding Information: The experimental work has been supported by the cluster of excellence RESOLV funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy ‐285 EXC‐2033—Projektnummer 390677874. The theoretical work at Emory was supported by NASA, Grant No. NNX16AF09G. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO) and supported by Laserlab‐Europe (grant agreement no. 654148, EU‐H2020).
• Keywords: Physical Sciences; CLUSTERS; INFRARED-SPECTROSCOPY; Science & Technology; ACCURACY; ENERGY SURFACE; LIQUID; MOLECULES; quantum calculations; potential surfaces; MONOMER; Chemistry, Multidisciplinary; helium nanodroplets; water clusters; IR spectroscopy; AB-INITIO; Chemistry
• Research Categories: Chemistry, General

Abstract

Using the helium nanodroplet isolation setup at the ultrabright free-electron laser source FELIX in Nijmegen (BoHeNDI@FELIX), the intermolecular modes of water dimer in the frequency region from 70 to 550 cm−1 were recorded. Observed bands were assigned to donor torsion, acceptor wag, acceptor twist, intermolecular stretch, donor torsion overtone, and in-plane and out-of-plane librational modes. This experimental data set provides a sensitive test for state-of-the-art water potentials and dipole moment surfaces. Theoretical calculations of the IR spectrum are presented using high-level quantum and approximate quasiclassical molecular dynamics approaches. These calculations use the full-dimensional ab initio WHHB potential and dipole moment surfaces. Based on the experimental data, a considerable increase of the acceptor switch and a bifurcation tunneling splitting in the librational mode is deduced, which is a consequence of the effective decrease in the tunneling barrier.