J. Phys. Chem. B 101 (1997) 3483-3493
Inner-Shell Excitation Spectroscopy of closo-Carboranes
Adam P. Hitchcock*,, Stephen G. Urquhart, Alex T. Wen, A. L. David Kilcoyne, Tolek Tyliszczak, Eckart Rühl,§ Nobuhiro Kosugi,# John D. Bozek, James T. Spencer,^ David N. McIlroy,Ñ and Peter A. DowbenÑ ,^
Department of Chemistry, McMaster University, Hamilton, Ontario, Canada, L8S 4MI
Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 91420
ÑCenter for Materials Research and Analysis, Department of Physics, University of Nebraska-Lincoln, Lincoln Nebraska 68588-0111,
§Institut für Physik Johannes Gutenberg-Universität Mainz D-55099 Mainz, Germany
# Institute for Molecular Science, Myodaiji, Okazaki Japan
^W. M. Keck Center for Molecular Electronics and the Department of Chemistry, Syracuse, University, Syracuse, New York 13244-4100
Received: July 29, 1996; In Final Form: November 7, 1996

Oscillator strength spectra in the region of B ls and C ls excitation of three isomeric carborane cage compounds [closo-1,2-orthocarborane, closo-1.7-metacarborane, closo-1,12-paracarborane (C2B10H12)] have been derived from inner-shell electron energy loss spectra (ISEELS) recorded under electric dipole-scattering conditions. Total ion yield spectra recorded at high resolution with synchrotron radiation are also reported. The spectral features are assigned on the basis of comparisons with special predictions derived from the results of ab initio and semiempirical (extended Hückel) molecular orbital calculations. The isomeric and core lever variations in the discrete core excitations are related to changes in orbital symmetries as well as variations in electron localization in these isomers. The ionization efficiency in the region of the B ls and C ls edges is derived.

ãAmerican Chemical Society, 1997