Potential energy surfaces for the reactions of the alkali metals M (Li, Na, K, Rb, and Cs) with Br2are computed using a simple semiempirical procedure. The calculations show that there is a vibrational barrier between M+Br2and M++Br2minus;along the Brndash;Br coordinate which plays an important role in the reaction. A potential well exists for all angles of approach of the metal to the molecule; this M+Br2minus;species is lower in energy than any product channel. The calculated ionic/covalent coupling matrix elements between M+Br2and M++Br2minus;agree well with the experimental values.
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