Strong spin-exchange recombination of three weakly interacting ^{7}Li atoms

Quantifying the nonuniversal three-body losses in ultracold atomic gases has been a long-standing problem. We go beyond earlier approaches to solve this problem by using a model that includes realistic pairwise interaction potentials and the exact three-atom spin structure. With this model we can successfully explain experimental observations for weakly interacting ^{7}Li and ^{87}Rb atoms. Capturing the exact spin structure, we are able to reveal a strong three-body spin-exchange recombination mechanism. In addition, we predict a regime of low three-body recombination rate in the ^{7}Li system that is advantageous for a variety of many-body experiments. This work opens avenues to study spin-involved few-body processes in quantum gases.