The metal 2p edge of Cu (left) and Zn (right) octaethyl porphyrin (top) and phthalocyanine (bottom). The Cu spectra are dominated by a pair of sharp transitions from the 2p 3/2 and 2p 1/2 levels into the 3d hole of Cu2 + at ∼931 and ∼951 eV. These are absent in the Zn spectra because the 3d shell is filled. The remaining much weaker transitions are assigned to nitrogen 2p and metal 4s states with very little metal 3d character.
Different experimental projections of the density of unoccupied states, obtained from the metal 2p edge, the N 1s edge, and inverse photoemission (reproduced from Ref. 41 for Cu-Pc and from Ref. 42 for Zn-Pc).
Determination of the lifetime broadening Γ of the unoccupied states by fitting the sharpest 2p 3/2 spectral features in Fig. 1. The line through the data is the sum of the features below. The peak widths increase linearly with energy as shown in Fig. 4.
The Lorentzian peak broadening (FWHM) versus the excess energy above the LUMO, obtained from the fits in Fig. 3. It increases linearly with the energy. The LUMO energy is 931.2, 931.9, 1021.9, and 1021.9 for Cu-OEP, Cu-Pc, Zn-OEP, and Zn-Pc, respectively. These results are used to realistically broaden theoretical energy levels in Fig. 5. Cu has open symbols, Zn has filled symbols, Pc has circles, and OEP has squares.
Partial density of unoccupied states calculated for the ground state by LDA. For Cu-Pc and Zn-Pc, the N 2p contributions from the inner and outer rings of nitrogens are similar to each other and have been added.
Article metrics loading...
Full text loading...