Berlin 2014 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 15: Experimental Techniques 3
MO 15.6: Vortrag
Donnerstag, 20. März 2014, 11:45–12:00, BEBEL SR144
Characterization of a 6 K Ring-Electrode Ion-Trap used for IR Photodissociation Experiments in a Triple Mass Spectrometer — •Tim Esser1, Nadja Heine1, and Knut R. Asmis1,2 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany — 2Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstrasse 2, D-04103 Leipzig, Germany
Mass-selective infrared photodissociation (IR-PD) spectroscopy combined with electronic structure calculations, is currently one of the most generally applicable techniques to determine the structure of gas phase cluster ions. To assure that the clusters are in their vibrational ground state they are typically buffer-gas cooled in a cryogenic ion trap. Here, we focus on the characterization of a linear ring-electrode radio-frequency (rf) ion-trap used in a 6K ion trap triple mass spectrometer. Preliminary results on the partially rotationally-resolved IR-PD spectrum of the singly hydrated ammonium ion, NH4+(H2O), allow to determine the rotational temperature as a function of the rf amplitude, buffer-gas pressure and store time. Apart from thermalization, the trap allows for bunching of the continuous ion beam and the attachment of messenger atoms or molecules. A genetic algorithm was developed, in order to automatically optimize the three sets of voltages, which are applied to the 12 pairs of ring electrodes during filling, storing and extraction. We further discuss the influence of the form of the trapping potential as well as the length of the store time on the size, shape and rotational temperature distribution of the ion packages.