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 Plenary Lecture Abstract 

Stephen F. Nelsen

   65th Birthday Symposium
Madison, Wisconsin
June 3-4, 2005

Stephen F. Nelsen

Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, WI  53706  nelsen@chem.wisc.edu

Using Koopmans' Theorem for Optical Spectra

Koopmans’ theorem (1934) states that ionization potentials are the negative of orbital energies. Photoelectron spectroscopy demonstratedthat this is an astonishingly good approximation. Edwin Haselbach’s group showed that when (and only when) little reorganization occurs upon electron loss, there is a remarkable correlation between the absorption spectrum of a radical cation and photoelectron spectrum of the neutral compound, although some bands are missing. But optical transitions are supposed to involve lots of configuration interaction, aren’t they? We applied the simple idea that Koopmans’ theorem will predict optical spectra of radical cations with the aid of Tim Clark (U. Erlangen) and Frank Weinhold (U.W.) in the mid 1980s to explain data on hydrazine radical cations, principally obtained by Si Blackstock, Tim Frigo, and Nathan Yumibe. Twenty years later, we have overcome our prejudice against aromatic compounds and radical anions and with the help of data collected by J. P. Telo (T.U. Lisbon) are realizing that many optical absorption spectra can be predicted and interpreted surprisingly simply.

Biographical Sketch

http://www.chem.wisc.edu/main/people/faculty/nelsen.html

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