Water is, to put it mildly, important. It's also peculiarly challenging to understand [here are a couple of informative sites: 1, 2]. Clusters of water molecules are useful prototype systems for understanding the microscopic structure, bonding, solvation properties, and phase transitions of this fascinating substance. Systematic observations of the variation of cluster properties with size can be translated into insights about molecular potentials and dynamics. We're working with water clusters to study:

• The evolution of electric dipole moment with cluster size
• The onset and development of solvation
• Pick-up of molecules by water clusters and implications for mass spectrometry
• Hydrated biomolecules

Water cluster beam apparatus

Water clusters are produced by expanding water vapor (alone or together with helium) through a small nozzle into vacuum. They are subsequently deflected by a strong inhomogeneous electric field, passed through a pick-up cell, or subjected to other probes. At the end, they are ionized by electron bombardment and detected by a quadrupole mass spectrometer.