TY  - JOUR
AU  - Sforzini, Jessica
AU  - Posseik, Francois
AU  - Tautz, Frank Stefan
TI  - Adsorption-induced symmetry reduction of metal-phthalocyanines studied by vibrational spectroscopy
JO  - Physical review / B
VL  - 96
IS  - 16
SN  - 2469-9950
CY  - Woodbury, NY
PB  - Inst.
M1  - FZJ-2017-06867
SP  - 165410
PY  - 2017
AB  - We investigate the vibrational properties of Pt- and Pd-phthalocyanine (PtPc and PdPc) molecules on Ag(111) with high-resolution electron energy loss spectroscopy (HREELS). In the monolayer regime, both molecules exhibit long-range order. The vibrational spectra prove a flat adsorption geometry. The redshift of specific vibrational modes suggests a moderate interaction of the molecules with the substrate. The presence of asymmetric vibrational peaks indicates an interfacial dynamical charge transfer (IDCT). The molecular orbital that is involved in IDCT is the former Eg lowest unoccupied molecular orbital (LUMO) of the molecules that becomes partially occupied upon adsorption. A group-theoretical analysis of the IDCT modes, based on calculated vibrational frequencies and line shape fits, provides proof for the reduction of the symmetry of the molecule-substrate complex from fourfold D4h to C2v(σv), Cs(σv), or C2 and the ensuing lifting of the degeneracy of the former LUMO of the molecule. The vibration-based analysis of orbital degeneracies, as carried out here for PtPc/Ag(111) and PdPc/Ag(111), is particularly useful whenever the presence of multiple molecular in-plane orientations at the interface makes the analysis of orbital degeneracies with angle-resolved photoemission spectroscopy difficult.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000412365700011
DO  - DOI:10.1103/PhysRevB.96.165410
UR  - https://juser.fz-juelich.de/record/838205
ER  -