NO2 adsorption on graphite at 90 K

High-resolution electron-energy-loss spectra (HREELS) and thermal-desorption spectra (TDS) are presented for NO2 adsorbed in the mono- and multi-layer regimes on graphite at 90 K. The TDS show a single desorption peak at 150 K at low coverages. A binding energy of 0.4 eV is estimated. At higher coverages, an additional peak due to multilayer desorption is observed at 140 K. The HREELS in the multilayer regime are fully compatible with a 3D solid structure of NO2 dimers. In the monolayer regime, a dimer interpretation is also favoured over monomer adsorption. The results are consistent with the dimers adsorbed with the molecular axis normal to the graphite surface.