Hot electron production and diffuse excited states in C70, C82, and Sc3N@C80 characterized by angular-resolved photoelectron spectroscopy

Abstract

Angular-resolved photoelectron spectroscopy using wavelength-tuneable femtosecond laser pulses is presented for a series of fullerenes, namely, C70, C82, and Sc3N@C80. The photoelectron kinetic energy distributions for the three molecules show typical thermal electron spectra with a superimposed peak structure that is the result of one-photon ionization of diffuse low-angular momenta states with electron density close to the carbon cage and that are related to so-called super atom molecular orbitals. Photoelectron angular distributions confirm this assignment. The observed structure is less prominent compared to the thermal electron background than what was observed in C60. It can be concluded that hot electron emission is the main ionization channel for the larger and more complex molecules for these excitation conditions.

Femtosecond X-ray-induced fragmentation of fullerenes

“…A fundamental understanding of the electronic structure and photo-initiated nuclear dynamics in these molecules can be achieved by probing relaxation channels and re-organizational dynamics of highly excited molecules. This will enable understanding of large organic molecules and carbon nanomaterials, important for optimizing their properties for use in molecular electronics and organic photovoltaics (46).…”

Super-atom molecular orbital excited states of fullerenes

“…The main difference in the photoelectron spectra is a broadening of the peak widths and a more prominent double-peak structure for the p-SAMO band due to the decreasing symmetry as the size of the fullerene cage is increased. The peak structure for the first s-and p-SAMO bands is almost completely smeared out for the endohedral fullerene, Sc 3 N@C 80 [9].…”

“…The details of the experimental techniques have been provided in previous publications [5,8,9] and will be only briefly described here. The original studies that reported the excitation and subsequent single-photon ionization of Rydberg states in C 60 were carried out with a combined linear time-of-flight photoelectron spectrometer and a time-of-flight mass spectrometer (MS) [5,10].…”

“…The emphasis was placed on the determination of the binding energies of the higher lying members of the Rydberg series that were well resolved using 800 nm laser pulses with 1.5 ps duration. In more recent studies, the time-of-flight photoelectron spectrometer was replaced by a velocity map imaging (VMI) spectrometer, illustrated in figure 2 [8,9]. This incorporates a position-sensitive detector consisting of a set of multichannel plates followed by a phosphor screen.…”

“…Adapted from [9]. Photoelectron spectra parallel and perpendicular to the laser polarization direction are compared for the different fullerenes whose β-values are plotted in figure 6, obtained at a wavelength of around 500 nm, in figure 7.…”