NITROGEN ADSORPTION ON Re(OOO1) STUDIED BY LEED, TPD, AES AND ELS

The interaction of nitrogen with a Re(OOO1) surface has been studied by low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS). Two LEED patterns have been observed upon adsorption of nitrogen on Re(OOO1). One, identified as the 4 x 1, is induced by N, exposure at 115 K and is related to the ordering of molecular nitrogen. Annealing the 4 x 1 phase to 300 K leads to the appearance of a 2x2 structure, an ordered structure formed from atomically adsorbed nitrogen, N,,. Two peaks are evident in the TD spectra foliowing N, exposure. A low temperature one, (I, at 160 K, whose desorption correlates with the disappearance of the 4 X 1 phase, is believed to correspond to physisorbed N,. A second feature, p, between 900 and 1300 K, desorbs with second order kinetics and corresponds to the recombination of NadJ. Adsorption of N, at 115 K induces sharp electron energy loss peaks at 5, 10, and 15 eV. These loss features disappear at 170 K upon desorption of the do N, and are interpreted to correspond to the electronic excitation of molecular nitrogen perturbed by the ReQJOO1) substrate. The e--beaminduced dissociation of molecularly adsorbed nitrogen on Re@OO1) is also discussed.