Atom-dimer exchange

The only alkali atom—dimer exchange reaction for which product energy distributions have been measured is... 

Let us first discuss a system which is traditional for optical pumping in the Kastler sense [106, 224, 226], namely an optically oriented alkali atom A (see Fig. 1.1) in a noble gas X buffer surrounding. It is important to take into account the fact that in alkali atoms, owing to hyperfine interaction, nuclear spins are also oriented. However, in a mixture of alkali vapor with a noble gas alkali dimers A2 which are in the 1SJ electronic ground state are always present. There exist two basic collisional mechanisms which lead to orientation transfer from the optically oriented (spin-polarized) atom A to the dimer A2 (a) creation and destruction of molecules in triple collisions A + A + X <—> A2 + X (6) exchange atom-dimer reaction... 

Despite an extensive study of the reactions of alkali dimers (see the reviews of Grice [208] and Herm [216]), there have been few direct measurements of energy disposal in these systems. The chemiluminescent reactions of oxygen and halogen atoms with alkali dimers have already been described [Sects. 3.1.7(c) and 3.1.8(b)], as have the alkali atom-alkali dimer exchange reactions [Sect. 3.1.2(b)], In this section we describe the chemiluminescent reactions of alkali diatomic molecules with halogen molecules. 

Hydrogen atoms in azolium ions can be removed easily as protons (e.g. 230—>232) exchange with deuterium occurs in heavy water. The intermediate zwitterion (e.g. 231) can also be written as a carbene, and in some cases this carbenoid form can be trapped or isolated as a dimer. 

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