Reactive scattering of alkali dimers K2+ I2, CH2I2, CHI3, CBr4

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Abstract
Angular distribution measurements of KX reactive scattering of a potassium dimer K2 beam by I2 and by a series of halomethane molecules are reported. The K2 + I2 reactive scattering is similar to that previously observed for K2 + Br2. The predominant reaction path yields K + KI + I with the K and KI product recoiling in the forward direction. However, the forward peak of the KI differential cross section is lower than that for K from K2 + I2 and is broader than that observed for KBr from K2 + Br2. This is attributed to slow dissociation of the I 2 - ion formed in the electron jump mechanism previously proposed for K2 + Br2. In the halomethane reactions, both alkali atoms of the K2 dimer become bound alkali halide molecules in all reactive collisions, despite the direct dynamics of the corresponding supersonic K atom reactions. Thus, these reactions provide compelling evidence for a second electron jump mechanism, previously proposed for the reactions of K2 dimers with polyhalide molecules. The differential cross sections for the K2 dimer plus halomethane reactions indicate an osculating collision complex with a lifetime at least comparable to its rotational period, perhaps much longer. This reaction complex is identified with the doubly ionic state formed by the second electron jump transition.