Fractional Quantization of Molecular Pseudorotation inNa3
Fractional quantization of the adiabatic pseudorotation in an isolated molecule is reported. This result, concerning the large-amplitude pseudorotation in ${2}^{2}{E}^{\ensuremath{'}}{\mathrm{Na}}_{3}$, constitutes the first direct verification of the adiabatic sign-change theorem, and also presents the most complete picture of the level structure and internuclear dynamics of a metal-atom cluster yet given.