Quantifying Hydrogen Bond Cooperativity in Water: VRT Spectroscopy of the Water Tetramer

Science  05 Jan 1996:
Vol. 271, Issue 5245, pp. 59-62
DOI: 10.1126/science.271.5245.59


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.