Formation of the acenaphthylene cation as a common CH-loss fragment in dissociative ionization of the PAH isomers anthracene and phenanthrene.

Polycyclic aromatic hydrocarbons (PAHs) are thought to be a major constituent of astrophysical environments, being the carriers of the ubiquitous aromatic infrared bands (AIBs) observed in the spectra of galactic and extra-galactic sources that are irradiated by ultraviolet (UV) photons. Small (2-cycles) PAHs were unambiguously detected in the TMC-1 dark cloud, showing that PAH growth pathways exist even at low temperatures. The processing of PAHs by UV photons also leads to their fragmentation, which has been recognized in recent years as an alternative route to the generally accepted bottom-up chemical pathways for the formation of complex hydrocarbons in UV-rich interstellar regions.

Unoccupied electronic band structure of pentagonal Si nanoribbons on Ag(110).

Silicon nanoribbons - one dimensional silicon structures with a pentagonal atomic structure and mixed sp- and sp-hybridisation - grow on Ag(110) upon deposition of silicon. These nanostructures are viewed as promising candidates for modern day electronics as they are comprised of the same element as today's semiconductor devices. Even though they have been studied extensively over the last decade, only little is known about their unoccupied band structure which is important for possible future optoelectronics, semiconductor, and spintronics applications.

Photoprocessing of large PAH cations.

In cosmic environments, polycyclic aromatic hydrocarbons (PAHs) strongly interact with vacuum ultraviolet (VUV) photons emitted by young stars. Trapped PAH cations ranging in size from 30 to 48 carbon atoms were irradiated by tunable synchrotron light (DESIRS beamline at SOLEIL). Their ionization and dissociation cross sections were determined and compared with TD-DFT computed photoabsorption cross sections.

Identification of the fragment of the 1-methylpyrene cation by mid-IR spectroscopy.

The fragment of the 1-methylpyrene cation, is expected to exist in two isomeric forms, 1-pyrenemethylium and the tropylium containing species We measured the infrared (IR) action spectrum of cold tagged with Ne using a cryogenic ion trap instrument coupled to the FELIX laser. Comparison of the experimental data with density functional theory calculations allows us to identify the isomer in our experiments. The IR Multi-Photon Dissociation spectrum was also recorded following the CH loss channel.