Anomalous Spectral Statistics of the Asymmetric Rotor Model

We investigate the spectral statistics of the asymmetric rotor model (triaxial rigid rotator). The asymmetric top is classically integrable and, according to the Berry-Tabor theory, its spectral statistics should be Poissonian. Surprisingly, our numerical results show that the nearest neighbor spacing distribution $P(s)$ and the spectral rigidity ${\mathrm{\Delta }}_3(L)$ do not follow Poisson statistics.