High‑precision loss measurements reveal orbital‑resolved p‑wave recombination in ultracold ⁶Li Spiral of light (Courtesy: iStock/Vika Suh) Physicists study ultracold lithium ‑ 6 because it is a fermionic isotope of lithium: its nucleus contains three protons and three neutrons, giving it a half ‑ integer total spin. This makes lithium ‑ 6 behave like other fundamental fermions such as electrons, protons, and neutrons, in contrast to lithium ‑ 7, which has an integer spin and is a boson. According to the Pauli exclusion principle, fermions cannot occupy the same quantum state, so lithium ‑ 6 provides a clean, controllable system for exploring how fermionic particles behave. It is also relatively easy to cool to ultracold temperatures, and its interactions can be tuned very precisely using magnetic fields. At these temperatures, atomic motion slows dramatically, allowing quantum mechanical effects to become directly observable.…