Femtosecond electron spectroscopy of coronene, benzo[GHI]perylene, and anthracene

Abstract

The large polycyclic aromatic hydrocarbon molecules coronene, benzo[GHI]perylene, and anthracene have been ionized with femtosecond laser pulses at low laser intensities and the ionization process studied with velocity map imaging spectroscopy, supplemented with ion yield measurements. The electron spectra of coronene and benzo[GHI]perylene are structureless. Based on fluence and pulse duration dependence measurements, it is shown that the electron spectra are not produced in field ionization processes, and the ionization mechanism is identified to be a quasithermal statistical electron emission, previously suggested for the fullerenes C(60) and C(70). The anthracene photoelectron spectra are dominated by above threshold ionization features, but with some indication of quasithermal ionization at longer pulses.

Probing excited electronic states and ionisation mechanisms of fullerenes

“…Experiments on cationic sodium clusters have also been interpreted by the transient thermal emission (or two-temperature) model 45,46 as have photoionisation studies of rare gas clusters 47 . Experiments have also been conducted identifying a similar ionisation mechanism for polycyclic aromatic hydrocarbons (PAHs) 48 . With increasing molecular size, a larger contribution from thermal electron emission was found.…”

Symmetry breaking and excitonic effects on optical properties of defective nanographenes

“…Indeed, smaller nanographene molecules, which might be known rather as polycyclic aromatic hydrocarbons (PAHs), have a long history of experimental and theoretical studies. 8,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] It is especially the case for those with odd-membered rings; PAHs with 5-membered rings are known as corannulene and those with 7-membered rings are 7-corannulene. Experimentally, their existence was confirmed and, theoretically, their atomic geometry and optical properties have been discussed in detail.…”

“…Experimentally, their existence was confirmed and, theoretically, their atomic geometry and optical properties have been discussed in detail. 14,18,19,21,[23][24][25][26][27][28] Although the PAHs have their defectless counterparts of almost the same size, the effect of the defect was not clarified through, for example, a comparative study. We consider that such a comparative study will be important in bridging the PAH chemistry and the nanographene chemistry.…”

Angular-resolved Photoelectron Spectroscopy of Superatom Orbitals of Fullerenes

“…It was first observed in 2001 that fs photoelectron spectra (PES) of small aromatic molecules [6,7] and fullerenes [8] show a rich Rydberg structure that appears largely independent of the laser excitation wavelength. For intense laser excitation, this structure is superimposed on a background of thermal electrons [8,9]. Well-resolved structure can be recorded even for vibrationally hot molecules due to the Á ¼ 0 propensity rule (based on Franck-Condon arguments and the structural similarity of the Rydberg states and the cation).…”