Osnabrück 2002 – wissenschaftliches Programm
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MS: Massenspektrometrie
MS 7: Moleküle, Cluster, Zerfälle und Reaktionen
MS 7.1: Vortrag
Freitag, 8. März 2002, 14:00–14:15, HS 02/E04
Carbon clusters for absolute mass measurements at ISOLTRAP — •K. Blaum1, G. Bollen2, F. Herfurth3, A. Kellerbauer3, H.-J. Kluge1, M. Kuckein4, E. Sauvan1, C. Scheidenberger1 und L. Schweikhard5 — 1GSI, Darmstadt — 2NSCL, East Lansing — 3CERN, Genève — 4TU, München — 5EMAU, Greifswald
The ISOLTRAP system installed at the on-line mass separator ISOLDE/CERN is a tandem Penning trap mass spectrometer, where the mass determination is carried out via determination of the cyclotron frequency of the stored ions. The magnetic field of the Penning trap is calibrated by measuring the well-known mass of a stable isotope. So far ISOLTRAP has been used for mass measurements on more than 200 radioactive isotopes. The high accuracy achieved for the masses (δ m/m ∼ 10−7) improved our knowledge of binding energies far from stability considerably. Recently, we have introduced a new method to check and increase the accuracy of these measurements by using singly charged carbon clusters Cn (n ≥ 2) for magnetic field calibration. The carbon cluster ions were produced externally by use of nanosecond laser desorption, fragmentation and photoionization of C60 at 532 nm. Based on the definition of the unified atomic mass unit as 1/12 of 12C, carbon clusters can be used as mass references for absolute mass measurements at ISOLTRAP, thereby eliminating the uncertainty of the mass of the reference ion by definition. In addition, the observation of cyclotron frequencies of different cluster sizes up to n = 20 allowed the study of systematic effects. An accuracy in mass measurement of δ m/m = 1.1 × 10−8 for the short lived 34Ar isotope could be demonstrated.