Current research topics
He droplets
Helium nanodroplets are used within almost all of our experiments. Helium droplets containing between 103 and 1013 He atoms are formed via supersonic expansion of helium at stagnation pressures of 20 bar and temperatures between 6 K and 12 K into ultra-high vacuum. Evaporative cooling leads to a constant temperature of 0.37 K inside the He droplet, which represents an ideal environment for numerous investigations due to the fact that all vibrational and most of the rotational degrees of freedom are frozen out at these low temperatures.
Contact:
Univ.-Prof. Dr. Paul Scheier
E-Mail: Paul.Scheier@uibk.ac.at
Phone: +43 (0)512 507 52660
ClusToF - Laser spectroscopy
In the “ClusToF” experiment, ionic species can be studied via laser spectroscopy. It employs a novel method for the efficient formation of complexes between ions and helium atoms where highly-charged, doped helium nanodroplets are collided with a surface. By overlapping the resulting ion beam with a laser beam of variable wavelength, these complexes can be dissociated which is monitored in a time-of-flight mass spectrometer. The current scientific focus is on the search for carriers of the diffuse interstellar bands, a group of some 500 interstellar absorption features, of which so far only a few were successfully assigned to a carrier, the buckminsterfullerene cation C60+. Furthermore, we are investigating the interaction between metal clusters and greenhouse gases to unravel the reaction mechanism at the molecular level, shedding light on their catalytic properties and potential applications in environmental mitigation strategies.
Hydra
In the “Hydra” experiment set up in 2023, the focus lies on the deposition of clusters on surfaces. Charged helium nanodroplets are also used in this setup. By doping the droplets with metallic samples, clusters grow on the charges in the droplets. These doped droplets are then shot onto a surface, causing the helium to evaporate on impact. However, the majority of the clusters remain on the surface. By changing the experimental parameters (droplet size, charge state of the droplets, type of dopant, duration of the coating process), surface coatings with different biological, physical and chemical properties can be produced. The samples are analyzed using various microscopy methods such as AFM (Atomic Force Microscope), STM (Scanning Tunneling Microscope) or TEM (Transmission Electron Microscope).
MR-TOF - Ion storage
A multireflectron time-of-flight (MR-ToF) is a mass spectrometer that has been in use for several decades. Due to its low cost and high mass resolution, it is a very popular choice when accurate mass determination is required. One of seven MR-ToFs, which were developed and built as part of a collaboration between the University of Darmstadt and the University of Greifswald, is now in operation in one of our laboratories. In addition to the advantages already mentioned, the MR-ToF also impresses with its versatility. At the moment we are using the multireflectron to capture and store helium nanodroplets (HNDs). Future plans for this device include implementing a laser to obtain time-resolved spectroscopy of dopants embedded in the HNDs (pump-probe experiments), as well as observing fluorescence, measuring reaction kinetics and also changing the experimental setup to take advantage of the high mass resolving power of the device.
Magnetron sputter deposition - Production & analysis of thin films
Magnetron sputter deposition allows for the production of thin metallic films onto a wide range of substrate materials. The combination of different source materials, such as titanium or gold, with varying discharge voltages and working pressures of argon and nitrogen offers a large degree of control over the growth of the film, which can be monitored through an in-situ quartz crystal microbalance.
Since the properties of thin films do not only depend on their composition, as it is the case for bulk materials, but are also strongly governed by their microstructure and layer thickness, controlling their growth delivers a powerful tool to optimise their application in surface modification and nanotechnology. The resulting surface properties can include, among others, adaption of the roughness, absorptivity, reflectivity and electrical conductivity which can be investigated with atomic force microscopy (AFM), scanning tunneling microscopy (STM), absorption spectroscopy and a four-point-probe.
