The formation and destruction of excited rare-gas dimers have been studied using resonance optical excitation of high-pressure gas mixtures containing Kr. From an analysis of the resulting emission, 19 reaction rate coefficients have been inferred. It is concluded that atom-atom interchange processes play a major role in rare-gas eximer formation, and that stepwise relaxation down the eximer vibrational ladder is less important than multistep relaxation due to atom-atom exchange in the excited eximer.Of the 29 reactions listed in Table I and the 23 reactions listed in Table I1 which could occur in mixtures of Kr with Ar or He, reactions (l), (3) + (4), and (18) have been measured by Turner [32] (as 1.3 X and 7.6 X in s-l, cm3/s, and cm6/s, as appropriate), while Hughes' has measured ky, kq, and k17 (5.3 X lo6, 5.5 X This paper describes spectroscopic measurements on mixtures of Kr and other gases when this mixture is excited by the 123.6-nm resonance line of Kr from an optically thick source. These measurements are interpreted to give the reaction rates of reactions (relative to the reaction rates of reactions Hughes [31] has measured k7 to be 5.3 X lo6 sl, k3 + kq = 5.5 X lo-?' , and h17 = 1.75 X 108. 4 X 1.8 X lo8).