THE MONOLAYER N2O/NACL(001) - AN FTIRS, LEED AND HAS STUDY

The adsorption of N2O on NaCl(100) single crystal surfaces was studied by means of Fourier transform infrared spectroscopy (FTIRS), low energy electron diffraction (LEED) and helium atom scattering (HAS) at sample temperatures around 77 K. The monolayer infrared spectra are similar to those of the isoelectronic CO2, exhibiting correlation field doublets for the symmetric and antisymmetric stretching vibrations nu(1) and nu(3). The observation of a doublet instead of the expected quartet absorption for the bending vibration nu(2) is surprising and due either to a very low absorber strength of the missing absorptions or to a bent rather than a linear adsorption geometry. The narrow line widths of all absorptions suggest a highly ordered structure and a preferred head-tail orientation of the NNO molecule. LEED measurements, which have been performed on adsorbate-covered NaCl single crystal surfaces for the first time, indicate a (2 X 1) superstructure of pg symmetry. This result is in agreement with the structure deduced from HAS experiments.