在气相条件下,氢与碘的反应半个多世纪以来一直被认为是一个双分子反应。几乎所有的物理化学教科书都拿它作为双分子反应的典型例子来讲授。然而,经过近几年的再实践、再认识,不论从实验事实或从理论分析来说,对这个问题的认识已经完全改观了。1967年 Sullivan 通过实验对氢-碘反应下列两种可能的机理进行了分析:H_2+I_2 k_1(?) 2HI (1)H_2+2I k_2(?) 2HI (2)在热化反应体系中,反应(1)与(2)从动力学角度来看是难以区分的。一方面,由于在碘分子与碘原子 In gas phase, the reaction of hydrogen with iodine has been considered a bimolecular reaction for more than half a century. Almost all physicochemical textbooks use it as a typical example of bimolecular reactions. However, after re-practicing in recent years, we have realized again that the understanding of this issue has been completely changed both in experimental facts and in theoretical analysis. In 1967 Sullivan experimentally analyzed the following two possible mechanisms of hydrogen-iodine reaction: H 2 + I 2 k_1 (?) 2HI (1) H 2 + 2I k 2 (?) 2HI (2) In the thermal reaction system, (1) and (2) are indistinguishable from a kinetic point of view. On the one hand, due to iodine molecules and iodine atoms