Pure Molecular Beam of Water Dimer.

Spatial separation of water dimers from water monomers and larger water clusters through the electric deflector is presented. A beam of water dimers with 93% purity and a rotational temperature of 1.5 K was obtained. Following strong-field ionization using a 35 fs laser pulse with a wavelength centered around 800 nm and a peak intensity of 1014 W/cm2, we observed proton transfer and 46% of ionized water dimers broke apart into hydronium ions H3O+ and neutral OH.

Note: Knife edge skimming for improved separation of molecular species by the deflector.

A knife edge for shaping a molecular beam is described to improve the spatial separation of the species in a molecular beam by the electrostatic deflector. The spatial separation of different molecular species from each other as well as from atomic seed gas is improved. The column density of the selected molecular-beam part in the interaction zone, which corresponds to higher signal rates, was enhanced by a factor of 1.5, limited by the virtual source size of the molecular beam.