Quantum chaotic behavior in vibro-roto-torsional levels of methanol and its isotopomers

A statistical analysis of experimental vibro-roto-torsional energy levels of CH3OH, CD3OH, CH3OD, 13CH3OH and 13CD3OH molecules is performed, calculating the nearest neighbor spacing level distribution and the Dyson–Metha Δ3(L). The interactions among the molecular internal motions are clearly proved by the departure of the statistics from the regular spectral behavior, in particular for the CH3OD molecule, for both the NNLSD and the Δ3(L). Increasing the torsional number n, an increasing in the irregularity of the spectra is also observed, accounting for a stronger interaction among the internal and global rotation. Strong differences are seen in the statistics of the various isotopomers, claiming for a future more accurate and conclusive study of the isotopic dependence in the global molecular energy levels dynamics.