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