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MO: Molekülphysik

MO V: HV V

MO V.1: Hauptvortrag

Donnerstag, 7. März 2002, 11:40–12:20, HS 01/E01

Electrodynamical Trapping - A Tool for Cold Gas Phase and Surface Studies Relevant to Astrophysical Chemistry — •Stefan Schlemmer — Institut für Physik, Technische-Universität Chemnitz, 09112 Chemnitz, Germany

Radio-Frequency quadrupole traps are widely used to store ions. In combination with mass spectrometric detection schemes electrodynamical trapping has proven to be a versatile tool for studying the kinetics and dynamics of ion molecule collisions at thermal and hyperthermal energies. Higher order multipole traps are used in our laboratory to perform studies at low temperatures and low densities. This environment is used to simulate the conditions of the interstellar medium (ISM) where ion-molecule reactions determine the abundances of the molecular species observed. Small differences in energy (fine-structure energy, rotational energy or differences in zero-point energy) play an important role on the outcome of these reactions. Combination with laser techniques are used in the experiments as a very sensitive tool for IR-ion-spectroscopy and kinetics. State-specific rate coeffcients are determined in order to unravel the role of, e.g., rotation and fine-structure in such collisions. Chemical probing is employed in various studies as another universal tool to distinguish between reaction products of the same mass. Electrodynamical trapping is also used to store even macroscopic bodies. Optical detection allows for a non-destructive, high-resolution mass spectrometry of small dust particles which are ubiquitous in the ISM. To date the precision is suffcient to record the adsorption or desorption of molecules from the surface with sub-monolayer resolution.