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Thursday, 04. April 2013 |
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15:15 – 16:15 |
Abstract :
In this talk an overview of fullerene photoionisation studies and their
relevance for understanding the ionisation dynamics and mechanisms of large
molecules will be given. When ionising with fs lasers, fullerenes, and other
conjugated molecules, show well-resolved peak structure in their photoelectron
spectra that can be attributed to single photon ionisation of a large range of
excited states, populated within the same laser pulse, thus providing a
“fingerprint” of the molecule. For fullerenes, strong peaks are observed that
are attributed to the excitation of SAMO states (super-atom molecular
orbitals), these are very simple hydrogenic-type orbitals that are centred on
the fullerene core rather than on the carbon atoms. They are a consequence of
the hollow nature of the molecule. New studies that combine fs Rydberg
fingerprint spectroscopy with angular-resolved photoelectron spectra obtained
using velocity map imaging and time-dependent density functional theory are
shedding new light on these states and the reason for their prominence in the photoelectron
spectra. Angular-resolved photoelectron spectroscopy can also provide
information on the timescale of electron emission and provide evidence for the
occurrence of thermal electron emission, responsible for a strong background
signal in the photoelectron spectra.