Infrared spectroscopy of physisorbed and chemisorbed N-2 in the Pt(111)(3x3)N-2 structure
Artikel i vetenskaplig tidskrift, 2007

Using infrared spectroscopy and low electron energy diffraction, we have investigated the adsorption of N-2, at 30 K, on the Pt(111) and the Pt(111)(1x1)H surfaces. At monolayer coverage, N-2 orders in commensurate (3x3) structures on both surfaces, and we propose that the unit cells contain four molecules in each case. The infrared spectra reveal that N-2 exclusively physisorbs on the Pt(111)(1x1)H surface, while both physisorbed and chemisorbed N-2 is detected on the Pt(111) surface. Physisorbed N-2 is the majority species in the latter case, and the two adsorption states show an almost identical uptake behavior, which indicates that they are intrinsic constituents of the growing (3x3) N-2 islands. An analysis of the infrared absorbance data, based on a simple scaling concept suggested by density functional theory calculations, supports a model in which the (3x3) unit cell contains one chemisorbed molecule in end-on atop configuration and three physisorbed molecules. We note that a classic ''pinwheel'' structure on a hexagonal lattice, with the end-on chemisorbed N2 molecules acting as ''pins,'' is compatible with this composition. (C) 2007 American Institute of Physics.







Kristian Gustafsson

Chalmers, Teknisk fysik

G. S. Karlberg

Danmarks Tekniske Universitet (DTU)

Stig Andersson

Göteborgs universitet

Journal of Chemical Physics

0021-9606 (ISSN) 1089-7690 (eISSN)

Vol. 127


Annan teknik