Dresden 2011 – scientific programme

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A: Fachverband Atomphysik

A 14: Interaction with VUV and X-ray light III

A 14.1: Invited Talk

Friday, March 18, 2011, 10:30–11:00, BAR 106

Synchrotron radiation spectroscopy of ions — •Alfred Müller — Institut für Atom- und Molekülphysik, Universität Giessen, Germany

Photoionization and -fragmentation of ions is studied by exposing suitable ionic targets to synchrotron radiation. The most common scenario for cross section measurements is the photon-ion merged-beam technique. Conventional mass and charge state analysis of accelerated ions provides well defined, clean targets for the monochromatized photons. All products of photon-ion interactions along the merge path of 0.3 to 1 m can be mass/charge separated with complete collection and almost 100 % detection efficieny. Accurate beam profile measurements allow for the determination of absolute cross sections. Scanning the photon energy in fine steps at resolving powers up to 40 000 delivers detailed spectroscopic information about excited states of the ions. Besides atomic ions also fullerene ions and endohedral fullerenes with encapsulated atomic ions have been studied. Time reversal symmetry relates photoionization to electron-ion recombination and provides new detailed insight into both processes. A particularly interesting subject of photon-ion studies is the response of endohedral fullerenes to photoabsorption by the atom encaged inside a carbon sphere. In comparison with a free ion, a significant redistribution of oscillator strengths is observed when the ion is encapsulated inside a fullerene cage. Also, evidence for containment resonances has been found. They arise from interference of photo-electron waves emitted by the central atom and then partially reflected back and forth by the fullerene sphere.