Electron-vibron coupling in halogenated acenaphthenequinone upon O K-edge soft x-ray absorption |
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Authors: | Schmidt Norman Clark Tim Urquhart Stephen G Fink Rainer H |
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Affiliation: | Interdisciplinary Center of Molecular Materials (ICMM), Universita?t Erlangen, Egerlandstrasse 3, D-91058 Erlangen, Germany. |
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Abstract: | We present high resolution oxygen K near-edge x-ray absorption spectra of the acenaphthenequinone (ANQ) derivative 3,8-dibromo-5,6-dichloro-ANQ (Br(2)Cl(2)-ANQ). The spectral features exhibit an almost identical vibronic fine structure compared to that shown by ANQ. The unequal distances of the vibronic levels as derived from the least-squares fit analysis of the vibronic progressions allows us to determine the anharmonicity of the excited state potentials involved. We conclude that a single vibrational progression couples to the resonant excitation of O 1s core electrons preferentially. Comparison of the two ANQ derivatives gives a clear indication that the vibronic mode corresponds to a C=O stretching mode, rather than coupling to a C-H mode as suggested previously. These conclusions are supported by density functional theory calculations. |
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