Magnetic quantum number resolved state-to-state chemistry

We extend state-to-state chemistry to a realm where besides vibrational, rotational and hyperfine quantum states magnetic quantum numbers are also resolved. For this, we make use of the Zeeman effect which energetically splits levels of different magnetic quantum numbers. The chemical reaction which we choose to study is three-body recombination in an ultracold quantum gas of $^{87}$Rb atoms forming weakly-bound Rb$_2$ molecules. Here, we find the propensity rule that the total $m_F$ quantum number of the two atoms forming the molecule is conserved. Our method can be employed for many other reactions and inelastic collisions and will allow for novel insights into few-body processes.