Insights, surprises, and puzzles of chemical reactions from ultracold chemistry

Nuclear spins are usually not thought to participate in chemical reactions. However, in the ultracold temperature regime, we have a new opportunity to examine this general statement with quantum mechanical details. In this talk, I will present our ongoing investigations into the roles of nuclear spins, quantum coherence, and entanglement in molecule-molecule reactions and atom-molecule collisions, utilizing a one-of-a-kind ultracold KRb molecule apparatus inspired from the original set of JILA KRb experiments 17 years ago. In addition to observing quantum interference in atom-exchange reactions [Science 384, 1117 (2024)], we hope to shed light on the puzzle of reaction complexes that live 5 orders of magnitude longer than expected.