Electron-stimulated dissociation of molecular N2 adsorbed on Ru(1Â 0Â 9): A TPD and IRAS investigation

Temperature programmed desorption (TPD) and infrared-reflection absorbance spectroscopy (IRAS) studies have been performed on the molecular adsorption state of N2 and its subsequent electron-induced dissociation on an atomically stepped Ru(1 0 9) single crystal surface. IRAS results revealed that N2 adsorbates exhibit only a single infrared absorption band at ∼2198-2196 cm−1 up to saturation, indicating an on-top configuration. TPD results show three distinct features (termed α1, α2, and α3), where at the lowest coverage, only α1 grows up to saturation with desorption at 184 K, followed by the α2 feature which desorbs at 136 K, and then, the surface saturates with the development of the α3 feature desorbing at 112 K. The IRAS results confirm that the three N2 desorption states comprise the molecular adsorption states on Ru(1 0 9) by the complete depletion of the IR band after annealing up to 200 K. The α1-N2 state is shown to be due to adsorption on the step sites of Ru(1 0 9). Electron-stimulated dissociation of the molecular N2 adsorbates produces two distinct recombinative, N(a) + N(a), desorption states (β1 and β2) between 400 and 800 K. The appearance of the β2 state is shown to be due to the coverage of atomic N produced by electron bombardment.