Dissociative recombination of polyatomic ions

The experimental data of Adams et al on products of the dissociative recombination of polyatomic ions are discussed and rationalized in terms of the valence bonds concerned. By combining the data with theoretical considerations branching ratios are derived. There are two main classes of saturated polyatomic ions: those for which the number of valences of the ionized atom is decreased by neutralization and those for which the number is increased. The hydride ions H 3 O + and H 4 N + are simple examples of the valence decrease class. It is reasoned that while H 3 O + cannot do likewise because of a difference in the OH and NH 2 relic radicals. The prediction is made that a bond between a pair of neutral atoms in an ion like CH 3 O + H 2 cannot be broken by dissociative recombination. Although the number of valences of an isolated C + ion increases on neutralization the dissociative recombination of polyatomic ions containing C + normally proceeds through a radiationless transition that causes a decrease.