Exoergic collisions of coldNa/emph>-Na

Abstract
We calculate rates for two exothermic excited-state collision processes involving sodium at ultracold temperatures. We predict that the rate for fine-structure changing collisions exceeds that of radiative redistribution with release of enough energy to cause loss from current optical traps. A semiclassical treatment is used which accounts for the frequency dependence of absorption and spontaneous emission in midcollision.