Berlin 2001 – wissenschaftliches Programm
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A: Atomphysik
A 5: Posters Tuesday (Photoionisation, Multi Photon Processes)
A 5.15: Poster
Dienstag, 3. April 2001, 12:30–15:00, AT3
Absolute photoionisation cross sections for ions of astrophysical relevance — •H Kjeldsen1, P A Andersen1, F Folkmann1, H Knudsen1, B Kristensen1, R L Brooks2, J B West3, and T Andersen1 — 1Institute of Physics and Astronomy, Univesity of Aarhus, Aarhus, Denmark — 2Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada — 3CLRC Daresbury Laboratory, Warrington WA4 4AD, United Kingdom
Absolute photoionisation cross sections have been measured for singly-charged ions of the astrophysically abundant elements C, N, O and Fe. The measurements were performed by merging a beam of the respective target ion with an intense beam of VUV synchrotron radiation from an undulator. In the case of O+ separate data sets were obtained for the 4S ground state and for the longlived 2D and 2P metastable states, since the fraction of metastable O+ ions could be changed by O+ + N2 charge-exchange reactions. The data have been compared with the most recent theoretical predictions using the R-matrix method. For C+, N+ and O+ the agreement between theory and experiment is rather good, however, very significant deviations are observed for the more complicated Fe+ cross section.