Berlin 2001 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
MO: Molekülphysik
MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes
MO 1.22: Poster
Monday, April 2, 2001, 12:30–15:00, AT3
Delayed ionization as a probe for competing fragmentation processes — •Martin Hedèn1, Frank Rohmund1, Alexander Bulgakov1, Raphael D. Levine2, and Eleanor E. B. Campbell1 — 1Dept. of Experimental Physics, Göteborg University/Chalmers University of Technology, SE-41296 Göteborg, Sweden — 2The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University, Jerusalem 91904, Israel
We investigate the delayed ionization of C60 on a time scale up to 50 µs. Our experimental ion signals, recorded after laser excitation with 3.7 eV photons, show a power law decrease for delay times up to 11 µs, beyond which the signal drops off faster. The data are in agreement with electron emisson rates measured by Deng and Echt.
In order to interpret our data we simulated the electron emission process. The result agrees with the experiment. For the calculations it was assumed that emission of electrons, loss of C2 and emission of black-body radiation from the excited C60 occur simultaneously. All these processes were described by rate constants which were reported in the literature. On the short time scale the experimental results can be reproduced if an energetic barrier for C2 loss of 10 eV is assumed. In the long delay regime, an additional C2 loss mechanism with a smaller energetic barrier has to be invoked. Both large and low energy barriers for C2 loss have been determined from different experiments. Our experiment and its interpretation show, that after laser excitation a transition between these two fragmentation regimes occurs which is reflected by the time dependence of the delayed ionization signal.