Soft X-ray emission and resonant inelastic scattering study of polycyclic hydrocarbons

This thesis comprises a detailed study of the electronic properties of the polycyclic hydrocarbonstetracene, perylene and coronene. The at room temperature grown organiclayers consisted of a up to several hundred nanometer thickness, and have been studiedwith the experimental techniques soft x-ray emission spectroscopy (SXES) and NEXAFS-spectroscopyby means of synchrotron radiation. In particular, resonant inelastic scattering(RIXS) was employed in order to obtain possible band structure or MO-symmetry informationof the studied systems. The studied materials consist of large organic molecules,evaporated under high vacuum an silicon wafers. The goal was to figure out, whether insidethese organic layers the hydrocarbon molecules polymerize and form a band structureor if the hydrocarbon molecules do not interact with each other and retain their originalmolecular like symmetry and behavior. The discrete peaks in the hydrocarbon NEXAFS-spectracould be assigned by comparison with the literature to chemical shifted C1s $\rightarrow \pi^{*}$transitions, caused by different chemical surrounded C-atoms. Hence, due to excitationan a certain $\pi$*-resonance only Cls-electrons of equal C-atoms can be excited, which leadsto a site selective excitation. The fluorescent decay of the created hole, which is as welllocalized an these former excited C-atoms was recorded energy dispersed in the SXE-spectrometer. This method is usually referred to as SXE. Therefore, the local MO-densitywas recorded. $\textit{Hartree-Fock}$ based ground state MO-calculations have been performed foreach molecule, in order to simulate the SXE-spectra. Good agreement between experimentand simulation was shown, under the strict retainment of symmetry selection rulesalong the transitions. This result states, that the different hydrocarbon molecules conservetheir symmetry and structure in an up to several hundred nanometer thick organic layer.Only in the region of the valence band maximum ($\pi$-states) weck indications for a banddispersion could be observed