The realization of isolated quantum systems within solid-state matrices is a pivotal challenge in quantum information science. This study demonstrates the existence of a “nano-vacuum” state in lithium-ion endohedral fullerene (Li+@C60·PF6–), where the encapsulated ion exhibits extreme magnetic isolation. Using ultrahigh field (18.79 T) solid-state NMR, we observed a 7Li line width of ∼50 Hz that remains invariant under magic angle spinning (MAS), indicating that the ion undergoes ultrafast isotropic motion (τc ≪ 10–5 s), which completely averages quadrupolar interactions. Most significantly, we report a record-breaking spin–lattice relaxation time (T1) of approximately 1068 s. This extraordinary lifetime is rationalized by a “relaxation blockade” mechanism: the absence of spin–orbit coupling prevents phonon scattering, while the rapid “roaming” of Li+ and the cooperative “plastic” rotation of external PF6– anions synergistically suppress dipolar and quadrupolar relaxation channels. These findings establish Li+@C60 as a ″thermodynamically open but magnetically closed″ system, offering a robust platform for quantum sensing.
Yoshida et al. (Mon,) studied this question.