Hydrogen dissociation on copper

The rotational and vibrational effects are strongly coupled, and reveal stronger rotational contributions at lower vibrational energy levels [20]. It was concluded [20] that vibrational energy is about 1.5 times more effective, and translational energy 2.5-3 times more effective, in promoting dissociation than rotational energy. 

The dependence of 50 on E for molecules in different vibrational and rotational states [19, 20] shown in Fig. 2 are characterised by an S-shape curve, where 50 saturates at high energy and falls exponentially as the energy decreases before flattening out at low energy. The sticking function is represented by a sigmoid curve based on an error function form  

There are two important differences between dissociation at Pt(l 1 1) and at the step sites introduced on Pt(5 3 3) which could account for these differences in Ts behaviour on Pt(l 11) and Pt(5 3 3) (Figs 7 and 8). The first contribution arises from the lower activation barrier at the (1 00) step sites (Fig. 4). For any fixed E, this will directly influence the tunnelling probability, and hence the reactivity. The 

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