Abstract
Far-infrared laser vibration-rotation tunneling spectroscopy was used to measure an intermolecular vibration (81.19198 wave numbers) of the isolated water (D2O) pentamer. Rotational analysis supports the chiral, slightly puckered ring structure predicted by theory. The experimentally deduced interoxygen separations for the water clusters up to the pentamer showed exponential convergence toward the corresponding distance in bulk phase water.