Karl Franzens University Graz
Graz University of Technology
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Karl Franzens University Graz | Graz University of Technology | |
Attosecond photochemistry: avoided crossings, conical intersections, and non-local core-hole dynamics Attosecond transient absorption is used to follow the dissociation and ionization dynamics in IBr, alkyl iodides, and ICl. In IBr and the alkyl iodides, a few fs visible or ultraviolet pulse accesses a dissociative state, and a broadband XUV attosecond probe pulse monitors the ensuing dynamics from the Franck-Condon region out to separated products. This experiment probes the change in electronic character of the dissociating molecule as it passes through avoided crossings (IBr, see Fig. 1) or, for the alkyl iodides, conical intersections. In the ICl experiments, a core-hole excitation on the I atom is created by the XUV pulse, and the resulting polarization decay is perturbed by a few-fs NIR pulse. Changes in the XUV absorption spectrum as a function of delay yield the lifetimes of the core-hole states, which are found to be 5 fs or less and depend on the alignment of the core hole. The results are interpreted in terms of non-local ionization, in which core-hole decay leads to ionization of the Cl atom.
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