Fast moving nuclei in Li19 clusters as evidenced by molecular beam ESR experiments

ESR spectra of free lithium clusters Li₁₁ and Li₁₉ were measured by a molecular beam method. The spectra show that the observed clusters are Li₁₀ + Li and Li₁₈ + Li, i.e., Li₁₀ and Li₁₈ with an atomic Li attached to them. The host cluster Li₁₈ in Li₁₉ is highly spin-polarized by the attached atom, and gives the spectrum a large number of equally spaced hyperfine-lines indicating 18 equivalent nuclei, which reveal fluid-like behavior of Li₁₈ at an estimated internal temperature of T = 102 K. The host cluster Li₁₀ in Li₁₁ is only weakly spin-polarized probably because Li₁₀ is an ordinary solid-like cluster.