Original scientific paper

An Overlapping Spheres Multiple Scattering Xa Study of the Perfluoro Effect on the Ionisation Potentials and Electron Transmission Spectra of Fluorosubstituted Benzenes

John E. Bloor ; Chemistry Department, University of Tennessee, Knoxville, TN 37996-1600, U.S. A.
Ronald E. Sherrod ; Chemistry Department, University of Tennessee, Knoxville, TN 37996-1600, U.S. A.

Abstract

The overlapping spheres multiple scattering Xu. method is
used to investigate the nature of the »perfluoro effect« through ·
ca'1culations on the ionisation potentials (IPs), electron affinities
(EAs), and elastic cross sections for electron scattering of benzene,
para-difluorobenzene, 1,3,5-trifluorobenzene, 1,2,4,5-tetrafluorobenzene
and hexafluorobenzene (HXFB). The results of the IP calculations
agree with experiment and, for the most part, with HAM/3
calculations but they differ considerably from assignments made
with the aid of Hartree-Fock minimal basis set calculations. The calculated
derivative curves for electron-molecule scattering agree with
the experimentally determined ones, but the detailed interpretation
of the elastic cross sections differs considerably from those given
previously. In previous work, all the resonances have been interpreted
in terms of the unoccupied valence orbitals but in this
work the second strong resonance, seen in all the fluorinated
benzenes except HXFB, is assigned to a temporary negative ion
state formed by electron capture in a dn type diffuse Rydberg
orbital. In HXFB there is only one strong resonance and this also
is assigned to electron capture in a dn type orbital. HXFB is the
only one of the series for which an experimental value for the
bound EA is known (1.8 eV). The theoretical value (1.7 eV) is in
good aggrement.

Keywords

Hrčak ID:

194070

URI

https://hrcak.srce.hr/194070

Publication date:

14.1.1985.

Visits: 616 *