We trap, store, and investigate ultracold atomic and molecular ions in a linear radio frequency (RF) ion trap. There are two cooling mechanisms which are employed: viscous drag cooling and sympathetic cooling. At present we are laser cooling Mg+ ions to milli Kelvin temperatures and observe ion crystals. The interaction of laser cooled Mg+ atomic ion crystals with simultaneously suspended, large molecular ion clouds are being studied. When in addition spectroscopy is applied to the cooled molecular ions this method promises to advance the understanding of molecular structures.
Rare earth endohedral fullerenes are chosen as a molecular object. Such
fullerenes are unique and intriguing complexes that combine atomic and
molecular properties in a single system. They are therefore called "super
atoms". The unique property of rare earth ions is that they have many intra configurational transitions, where the configuration of the electron orbitals is not changed, so the size and shape of the electron cloud is practically unaffected. Hence the coupling between the optical transition and the rovibronic energy levels of the fullerene is expected to be weak. This expectation is strenghtened by the fact that even when rare earth ions are encapsulated in glass or crystal structures their intra confugurational transitions exhibit relatively narrow optical lines. The fluorescence from the coolant ions and/or the endohedral ions will make it possible to monitor the time evolution time of the various cooling process by observing the Doppler width of the radiation. Eventually even laser cooling of the metallo fullerene molecule via its coupling the endrohedral ion could be possible. The spectroscopy of the rare earth endohedral fullerenes contributes to the understanding of these promising compounds, which could be used as a basis for laser materials, provide new high temperature superconductors, solid state devices and microprobes with chemical resolution.
We have also developed a versatile parametric excitation scheme for exciting the ion-motion and a novel trapping device, which we labeled the linear combined trap.
