Angular-resolved fs Photoelectron Spectroscopy of Fullerenes: giant atoms or hot metal spheres?

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.