J. Phys. IV France 7 (1997) C2-163-C2-164
Core Excitonic Effects in the NEXAFS Spectra of Condensed Polycyclic Aromatic HydrocarbonsH. Oji1, R. Mitsumoto1, E. Ito1, H. Ishii1, Y. Ouchi1, K. Seki2 and N. Kosugi3
1 Dept. Chem., Faculty of Science, Nagoya Univ., Chikusaku, Nagoya 464-01, Japan
2 Dept. Chem., Faculty of Science, Nagoya Univ., Chikusaku, Nagoya 464-01 Japan
3 Institute for Molecular Science, Myodaiji, Okazaki 444, Japan
NEXAFS spectra of three condensed aromatic hydrocarbons, chrysene, perylene, and coronene, were measured and analyzed in particular emphasis on the effect of core excitonic effect as the origin of modification of the observed spectra from density of unoccupied states (DOUS). The comparison of the observed spectra with reported inverse photoemission spectra and calculated DOUS showed poor correspondence, indicating large deviation between the NEXAFS spectra and DOUS. On the other hand, the simulation of the spectra by ab inito MO calculations, using the hole potential method, reproduced the experimental results well. The analysis of the results of MO calculations revealed that core excitonic effect significantly depends on the site of the excited atom and the character of the unoccupied orbital, making the observed spectra much different from the DOUS.
© EDP Sciences 1997