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Hannover 2003 – wissenschaftliches Programm

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MO: Molekülphysik

MO 12: Poster II

MO 12.3: Poster

Donnerstag, 27. März 2003, 16:00–18:30, Lichthof

Investigation of protonated water clusters in a variable temperature 22-pole ion trap — •Oskar Asvany1, Stephan Schlemmer1, Dieter Gerlich1, Y.S. Wang2, C.H. Tsai2, Y.T. Lee2, J.C. Jiang2, and H.C. Chang21Institut für Physik, TU Chemnitz, 09112 Chemnitz — 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan

Protonated water clusters play an important role in atmospheric chemistry and in interstellar space. A variable temperature 22-pole ion trap has been applied to kinetic and spectroscopic investigations of protonated water clusters, H+(H2O)n, produced from a supersonic expansion. Using low-pressure He buffer gas for collisional thermalization, refrigeration of the ion trap allows a good control of the cluster temperature over the range 80 - 350 K. This method provides an accurate means of determining the dissociation energies of the cluster ions by measuring their dissociation rates as a function of temperature and calculating their internal energies from vibrational frequencies provided by density functional theory. Results of the thermochemical measurements at well-defined cluster temperatures are given for H+(H2O)n, n = 4-10. The feasibility of using the ion trap to acquire temperature-dependent infrared spectra is discussed. Future experiments with a similar 22-pole ion trap machine will explore the deuteration of protonated water clusters in collisions with HD.

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