X-ray absorption and resonant Auger spectroscopy of O{sub 2} in the vicinity of the O 1s{yields}{sigma}* resonance: Experiment and theory
- Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala (Sweden)
- Department of Theoretical Chemistry, Roslagstullsbacken 15, Royal Institute of Technology, S-106 91 Stockholm (Sweden)
- Institute of Chemical Physical Processes-CNR, via Moruzzi 1, 56124, Pisa (Italy)
- Department of Chemistry, University of Ferrara, via Borsari 46, 44100 Ferrara (Italy)
- Department of Synchrotron Radiation Research, Institute of Physics, University of Lund, Box 118, S-221 00 Lund (Sweden)
- Japan Synchrotron Radiation Research Institute, Sayo-gun, Hyogo 679-5198 (Japan)
- Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526 (Japan)
- Department of Physics, Sophia University, Tokyo 102-8554 (Japan)
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 (Japan)
We report on an experimental and theoretical investigation of x-ray absorption and resonant Auger electron spectra of gas phase O{sub 2} recorded in the vicinity of the O 1s{yields}{sigma}* excitation region. Our investigation shows that core excitation takes place in a region with multiple crossings of potential energy curves of the excited states. We find a complete breakdown of the diabatic picture for this part of the x-ray absorption spectrum, which allows us to assign an hitherto unexplained fine structure in this spectral region. The experimental Auger data reveal an extended vibrational progression, for the outermost singly ionized X {sup 2}{pi}{sub g} final state, which exhibits strong changes in spectral shape within a short range of photon energy detuning (0 eV>{omega}>-0.7 eV). To explain the experimental resonant Auger electron spectra, we use a mixed adiabatic/diabatic picture selecting crossing points according to the strength of the electronic coupling. Reasonable agreement is found between experiment and theory even though the nonadiabatic couplings are neglected. The resonant Auger electron scattering, which is essentially due to decay from dissociative core-excited states, is accompanied by strong lifetime-vibrational and intermediate electronic state interferences as well as an interference with the direct photoionization channel. The overall agreement between the experimental Auger spectra and the calculated spectra supports the mixed diabatic/adiabatic picture.
- OSTI ID:
- 21024773
- Journal Information:
- Journal of Chemical Physics, Vol. 128, Issue 6; Other Information: DOI: 10.1063/1.2831920; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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