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MS: Fachverband Massenspektrometrie

MS 3: Präzisionsmassenspektrometrie, Ionenfallen, FT-IZR-MS, Moleküle, Cluster III

MS 3.8: Vortrag

Montag, 2. März 2009, 18:00–18:15, VMP 8 R05

Cryogenic hydrogen ions and chemical probing spectroscopy in rf ion cages — •Max H. Berg¹, Annemieke Petrignani¹, Dennis Bing¹, Holger Kreckel², and Andreas Wolf¹ — ¹Max-Planck Institut fuer Kernphysik, Heidelberg D-69117 — ²Columbia University, New York, NY 10027, USA

Radio frequency ion cages in the 22-pole geometry are well established tools for confining molecular ions in an almost field-free space, providing distinctly lower ion micromotion than standard Paul traps. We are applying these devices for the cryogenic cooling of H₃⁺ ions by He buffer gas down to the lowest rotational levels. H₃⁺ plays an important role in astrophysical and technical hydrogen plasmas, and is also a benchmark for quantum mechanical calculations of rovibrational energy levels of polyatomic molecules. For rovibrational spectroscopy, the conventional absorption method is a cumbersome approach as densities are low and H₃⁺ rovibrational transitions are weak. A much more efficient detection method adapted to the cold multipole traps is to probe photon absorption by laser induced chemical reactions. The reaction products are detected via a mass spectrometer with near unity efficiency. This method revealed in the latest measurements the weakest H₃⁺ rovibrational transitions observed to date, accessing vibrational levels more than 1.6 eV above the ground state.