Temperature programmed desorption (TPD) and infrared-reflection absorbance spectroscopy (IRAS) studies have been performed on the molecular adsorption state of N 2 and its subsequent electron-induced dissociation on an atomically stepped Ru(109) single crystal surface. IRAS results revealed that N 2 adsorbates exhibit only a single infrared absorption band at ∼2198–2196cm −1 up to saturation, indicating an on-top configuration. TPD results show three distinct features (termed α 1 , α 2 , and α 3 ), where at the lowest coverage, only α 1 grows up to saturation with desorption at 184K, followed by the α 2 feature which desorbs at 136K, and then, the surface saturates with the development of the α 3 feature desorbing at 112K. The IRAS results confirm that the three N 2 desorption states comprise the molecular adsorption states on Ru(109) by the complete depletion of the IR band after annealing up to 200K. The α 1 -N 2 state is shown to be due to adsorption on the step sites of Ru(109). Electron-stimulated dissociation of the molecular N 2 adsorbates produces two distinct recombinative, N(a)+N(a), desorption states (β 1 and β 2 ) between 400 and 800K. The appearance of the β 2 state is shown to be due to the coverage of atomic N produced by electron bombardment.