Observation of state-to-state hyperfine-changing collision in a Bose-Fermi mixture of ${}^6$Li and ${}^{41}$K atoms

Hyperfine-changing collisions are of fundamental interest for the studying of ultracold heteronuclear mixtures. Here, we report the state-to-state study of the hyperfine-changing-collision dynamics in a Bose-Fermi mixture of ${}^6$Li and ${}^{41}$K atoms. The collision products are directly observed and the spin-changing dynamics is measured. Based on a two-body collision model, the experimental results are simultaneously fitted from which the spin-changing rate coefficient of $1.9(2)\times {10}^{-12}\mathrm{c}{\mathrm{m}}^3\cdot {\mathrm{s}}^{-1}$ is gained, being consistent with the multi-channel quantum defect theory calculation. We further show that the contact parameter of ${}^6$Li-${}^{41}$K mixture can be extracted from the measured spin-changing dynamics. The obtained results are consistent with the first order perturbation theory in the weakly-interacting limit. Our system offers great promise for studying spin-changing interactions in heteronuclear mixtures.