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Appendix C: Hartree-Fock orbital energies versus photoelectron energies

We wish to compare vertical ionization energy of core and valence electrons determined experimentally using photoelectron spectroscopy with eFF electron energies. However, photoelectron spectroscopy measures ionization from molecular orbitals, which are delocalized, in contrast to the localized electrons in eFF. To validate eFF, we use Hartree-Fock (6-311g** basis) as an intermediate reference theory. First, we relate Hartree-Fock orbital energies to the experimental ionization potentials:

$\displaystyle \mathrm{E(IP) = 0.777 E(HF) + 2.386 eV}.$ (4.17)

Then, we compare eFF electron energies to localized Hartree-Fock orbital energies.

Table 4.9: eFF computed valence ionization potentials are close to ones estimated by Hartree-Fock (corrected energies, see text).
  Valence IP (eV)
  eFF HF/ $ \mathrm{local^{*}}$ difference
methane CH 13.98 16.02 -2.04
ethane CH 13.82 15.99 -2.17
neopentane CH 13.83 15.98 -2.15
adamantane CH 13.84 15.99 -2.15
adamantane CH 13.85 15.95 -2.10
       
average 13.86 15.99 -2.12
       
ethane CC 17.75 16.76 1.00
neopentane CC 15.77 16.77 -1.00
adamantane CC 16.75 16.68 0.07
       
average 16.76 16.74 0.02



Table 4.10: eFF underbinds core electrons, making less energy available for Auger decay.
  Core IP (eV)
  eFF expt difference
methane 239.20 290.84 -51.65
ethane 237.07 290.71 -53.64
neopentane (C) 230.52 290.35 -59.82
neopentane ( $ \mathrm{CH_{3}}$) 237.30 290.53 -53.23
adamantane (CH) 233.92    
adamantane ( $ \mathrm{CH_{2}}$) 235.98    
       
average, first four 236.02 290.61 -54.59



Table 4.11: Comparison of Hartree-Fock orbital energies with vertical ionization potentials from photoelectron spectroscopy [69].
  Valence IP (eV)
  HF expt
methane 25.71 22.9
  14.86 15.0
     
ethane 27.71 23.9
  22.94 20.4
  16.24 15.8
  13.83 13.3
  13.24 12.1
     
neopentane 30.01 25.1
  25.30 21.9
  19.91 17.8
  16.63 15.2
  15.05 14.0
  13.90 12.4
  12.30 11.5



next up previous contents
Next: Bibliography Up: Development of an electron Previous: Appendix B: Derivation of   Contents
Julius 2008-04-29