Initial sticking probability of O2 on Cu(4 1 0)

We present here a supersonic molecular beam investigation of the initial sticking probability (S0) for the O2/Cu(4 1 0) system. Over the temperature range between 130 and 800 K adsorption occurs dissociatively and S0 increases up to ∼0.7 with beam energy, indicating that the process is activated. S0 is larger for angles corresponding to molecules impinging on the step rises, implying that defects are more reactive than terrace atoms. The saturation value of S0 is however lower than for the parent low Miller index surfaces; this indicates that the reactivity at nanosized terraces is reduced compared to extended Cu(1 0 0) faces. A precursor mediated adsorption path is observed at the lowest translational energy (Ei) below 150 K, as in the case of O2/Cu(1 1 0) and at variance with O2/Cu(1 0 0). At low T and higher energy and for all Ei at T > 150 K, adsorption occurs directly, yielding a sticking probability independent of surface temperature.