Chemistry Reference
In-Depth Information
a
g
(2.08 eV)
b
3g
(2.58 eV)
a
u
(2.94 eV)
b
2g
(3.07 eV)
b
3u
(3.61 eV)
b
2u
(3.26 eV)
b
2u
(3.86 eV)
Figure 6.15. Schematic representation of the relevant TTF unoccupied MOs for
the analysis of the NEXAFS spectra of TTF and TTF-TCNQ. The symmetry labels
are those appropriate for the
D
2
h
symmetry. The energy values given (in eV) are
relative to those of the HOMO of TTF in the isolated TTF molecule. Reprinted
with permission from J. Fraxedas, Y. J. Lee, I. Jimenez, R. Gago, R. M. Nieminen,
P. Ordejon and E. Canadell,
Physical Review B
,
68
, 195115 (2003). Copyright
(2003) by the American Physical Society.
In fact, the
d
-contributions extend over all the energy range of interest so that even
if the
p
-contributions are dominant, there is always some
d
-contribution of the
appropriate symmetry and, as a consequence, the levels are going to be visible to
some degree in the S2
p
spectra.
The unoccupied TTF MOs are schematically shown in Fig. 6.15. The energy
values associated with the orbitals are those calculated for a single molecule with the
same geometry as for the neutral solid. The symmetry labels are those appropriate
for idealized
D
2
h
symmetry. For simplicity, the sulfur
d
orbital contributions have
not been shown in these schematic drawings.
