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Observation of the Low‐Frequency Spectrum of the Water Dimer as a Sensitive Test of the Water Dimer Potential and Dipole Moment Surfaces
Author(s) -
Schwan Raffael,
Qu Chen,
Mani Devendra,
Pal Nitish,
Meer Lex,
Redlich Britta,
Leforestier Claude,
Bowman Joel M.,
Schwaab Gerhard,
Havenith Martina
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201906048
Subject(s) - water dimer , dipole , intermolecular force , overtone , ab initio , molecular physics , quantum tunnelling , chemistry , dimer , atomic physics , ab initio quantum chemistry methods , molecule , physics , hydrogen bond , spectral line , condensed matter physics , quantum mechanics , organic chemistry
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.