The miniaturization of mechanical and electronic components to the size range of 1 to 100 nm, corresponding to an arrangement of 10 to 1000 atoms in a row is an obvious achievement of nanotechnology. However, an even more important aspect than the shrinking in space is given by the changes of mechanical, thermal, electric, magnetic, and optical properties with the size of such atomic arrangements that are caused by the effects of quantum physics. Objects consisting of fewer than several thousand atoms or molecules are called atomic or molecular clusters, respectively. The surface to volume ratio of a cluster and the laws of quantum mechanics govern which color of light is absorbed and whether electrons are free to move inside the cluster. So, these properties change with cluster size even though the clusters are made of the same elements. Since research on clusters has shown how phase transitions as well as electric and magnetic properties of finite size matter can be described, scientists try to tailor building blocks for new materials according to different applications. The composition of new building blocks can be achieved by different methods that need to include the appropriate diagnostics to determine the atomic structure, the optical absorption, the magnetic dipole moment etc. Low temperatures are essential for a controlled formation process that would be disturbed by thermal motion.
At the Institute of Experimental Physics, methods have been developed to dope superfluid helium droplets of 0.4 Kelvin temperature with single atoms and molecules to produce cold new aggregates whose properties are analyzed by mass and laser spectroscopy as well as electron spin resonance. In addition, surface physics diagnostics are available. In this project, cold clusters will be prepared from various metallic species and studied at a temperature below 1 Kelvin. At such low temperature, the formation of large magnetic dipoles, the change of electronic structure and the manifestation of superconductivity in nanosized metal aggregates are of high interest. Isolated nanoclusters are to be deposited onto a cold surface. The prepared surface structures will be investigated by scattering methods and compared with the surface of conventional bulk material. The interaction of the novel surfaces with molecular gases will be tested for their potential use as catalysts.