C. Mainka et al., A MULTITECHNIQUE SPECTROSCOPIC INVESTIGATION OF THE ADSORPTION OF PYROMELLITIC DIANHYDRIDE (PMDA) ON PT(111), Zeitschrift für physikalische Chemie, 198, 1997, pp. 221-243
Citations number
55
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The adsorption of pyromellitic dianhydride (PMDA) on the Pt(111) surfa
ce was studied by near edge X-ray absorption fine structure spectrosco
py (NEXAFS), X-ray photoelectron spectroscopy (XPS), ultraviolet photo
electron spectroscopy (UPS) and temperature programmed desorption (TPD
). The XPS data verify a non-dissociative adsorption for the monolayer
in agreement with Fourier Transform Infrared Absorption Spectroscopy
(FT-IRAS) data reported previously. Adsorption leads to considerable b
roadening of the pi resonances in the carbon K-edge NEXAFS-spectra wh
ich is an indication for a strong adsorbate-substrate interaction. An
analysis of the polarization dependence of the NEXAFS resonances confi
rms the presence of flat-lying molecular PMDA on the surface, but addi
tionally indicates a strong (approximate to 20 degrees for the anhydri
de units) out of plane distortion of the molecules. UPS on gas phase P
MDA reveals that the HOMO is located at 11.8 eV below E(Vac). TPD spec
tra recorded at different molecular masses reveal that above 340 K mon
olayer PMDA undergoes competing decomposition and desorption; decompos
ition to a surface carbon residue is complete by 550 K.