Science. 1994 Jan 21;263(5145):365-7. doi: 10.1126/science.263.5145.365.
It has long been postulated that gas-surface chemical reactions can occur by means of two distinct mechanisms: direct reaction on a single gas-surface encounter or reaction between two adsorbed species. It is shown here that these mechanisms have distinct dynamical signatures, as illustrated by the reaction of hydrogen with chlorine on gold(111). The direct reaction product leaves the surface with a high kinetic energy in a narrow angular distribution that displays a "memory" of the direction and energy of the incident hydrogen atom. The indirect reaction product has a near-thermal energy distribution and an angular distribution that is close to that of a cosine function.
长期以来，人们一直假设气体-表面化学反应可以通过两种不同的机制发生：在单次气体-表面碰撞上的直接反应或两种吸附物种之间的反应。这里表明，这些机制具有明显的动力学特征，如图所示，氢与氯在金(111)上的反应。直接反应产物以窄角分布从表面高速离开，该角分布显示了入射氢原子的方向和能量的“记忆”。间接反应产物具有近热动能分布和接近余弦函数分布的角分布。
