One of the most useful established methods to obtain structural information for isolated molecular ions is to determine their rotationally averaged collision cross sections and to compare these to predictions from a structural model. We use a combination of ion mobility mass spectrometry (for the experimental collision cross section determination under variable temperature conditions) and density functional theory with a genetic algorithm mininum search (for the structural models; often in collaboration with KIT quantum chemists). This approach is particularly suitable for the structure determination of charged (metal) cluster species - which we study size-selectively up to about 20 atoms by ion mobility. Presently, we are working on clusters of bismuth and lanthanum. The cluster ion mobility work is complementary to our electron diffraction studies - often applied to larger clusters of the same element.
"Structures and Energetics of Small Lead Cluster Ions", Rebecca Kelting, Robin Otterstätter, Patrick Weis, Nedko Drebov, Reinhart Ahlrichs and Manfred Kappes, J. Chem. Phys., 2011, 134, 024311.