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:

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