Attachment cross sections of protonated water clusters.

The attachment of water molecules onto size selected protonated water clusters has been experimentally investigated. Absolute attachment cross sections are measured as a function of cluster size, collision energy, and initial cluster temperature. Although thermal evaporation is ruled out in our experiment, attachment cross sections become significantly smaller than hard sphere cross sections as the collision energy increases.

Sticking properties of water clusters.

Absolute attachment cross sections of single water molecules onto mass-selected protonated water clusters have been measured in the 30-200 size range and for collision energies down to approximately 50 meV. The major surprise is that the attachment cross sections are always smaller or equal to the hard sphere cross section. The attractive interaction between water molecules and charged water nanodroplets does not enhance the sticking probability as expected.

A novel experimental method for the measurement of the caloric curves of clusters.

A novel experimental scheme has been developed in order to measure the heat capacity of mass selected clusters. It is based on controlled sticking of atoms on clusters. This allows one to construct the caloric curve, thus determining the melting temperature and the latent heat of fusion in the case of first-order phase transitions.