title: Quantifying hydrogen bond cooperativity in water:  VRT spectroscopy of the water tetramer.
abstract: Measurement of the far-infrared vibration-rotation tunneling spectrum of the perdeuterated water tetramer is described.  Precisely determined rotational constants and relative intensity measurements indicate a cyclic quasi-planar minimum energy structure, which is in agreement with recent ab initio calculations.  The O-O separation deduced from the data indicates a rapid exponential convergence to the ordered bulk value with increasing cluster size.  Observed quantum tunneling splittings are interpreted in terms of hydrogen bond rearrangements connecting two degenerate structures.
authors.affiliation: Department of Chemistry, University of California at Berkeley 94720, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Cruzan
authors.forename: L B
authors.initials: LB
authors.lastname: Braly
authors.forename: K
authors.initials: K
authors.lastname: Liu
authors.forename: M G
authors.initials: MG
authors.lastname: Brown
authors.forename: J G
authors.initials: JG
authors.lastname: Loeser
authors.forename: R J
authors.initials: RJ
authors.lastname: Saykally
mesh_terms: D017666:Deuterium Oxide / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D019265:Spectroscopy, Near-Infrared; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D006859:Hydrogen; D017666:Deuterium Oxide; D010100:Oxygen