title: Two-dimensional Raman-terahertz spectroscopy of water.
abstract: Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water.
authors.affiliation: Department of Chemistry, University of Zurich, CH-8057 Zurich, Switzerland.
authors.forename: Janne
authors.initials: J
authors.lastname: Savolainen
authors.forename: Saima
authors.initials: S
authors.lastname: Ahmed
authors.forename: Peter
authors.initials: P
authors.lastname: Hamm