Resonant CKα X-ray emission of some carbon allotropes and organic compounds

The applications of resonant soft X-ray emission spectroscopy on a variety of carbon systems have yielded characteristic fingerprints. With high resolution monochromatized synchrotron radiation excitation, resonant inelastic X-ray scattering has emerged as a new source of information about electronic structure and excitation dynamics. The selectivity of this excitation, in terms of energy and polarization, has also facilitated studies of emission anisotropy. Various features observed in resonant emission spectra have been identified and studied. In the ordered wide-band systems (e.g., diamond and graphite), momentum conservation of resonant inelastic X-ray scattering has been observed, and the aspect of using this for studies of band dispersion is pointed out. In the molecule-like systems, such as C-60, C-70, benzene and derivatives, conjugated polymers, symmetry selection rules have been established, and deviations from the symmetry selection rules observed have been interpreted in terms of dynamical symmetry breaking. In the studies of pi-conjugated polymers, it has been found that the benzene-ring has a strong identity as a building block in some of the conjugated polymers. Isomeric dependence was able to be clarified in the studies of polypyridine. The doping induced protonation effect has been observed as the depletion of the upmost occupied valence band in the doped polyaniline. (C) 2000 Elsevier Science BN. All rights reserved.