Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10674960 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms | 2005 | 13 Pages |
Abstract
A merged-beam set-up for absolute measurements of photoionization cross-sections of ions is described. The facility is capable of recording cross-sections as low as 10â19Â cm2 and has been used to study a large number of singly- and multiply-charged, atomic and molecular, positive and negative ions. It is based on a synchrotron radiation beam line fitted with an undulator at the storage ring ASTRID and a low-energy (â¼2Â keV) ion beam line. Photons in the energy range 15-200Â eV are merged co-linearly with the target ions over a distance of 50Â cm, and the absolute photoionization cross-section is determined from the resulting photoion yield with a typical accuracy of 10%. Different types of ion sources are available, thus permitting a large number of positive and negative, atomic and molecular, singly- and multiply-charged ions to be investigated. Emphasis is put on accurate determination of the absolute cross-sections, requiring calibration of photodiode and particle detectors together with measurements of the photon-ion overlap.
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Authors
Henrik Kjeldsen, Finn Folkmann, Jan van Elp, Helge Knudsen, John B. West, Torkild Andersen,