ROTATIONAL TUNNELING SPECTRA FOR MANY COUPLED METHYL ROTORS

The rotational tunnelling spectrum for a (cyclic) chain of four or more coupled methyl groups appears to look (qualitatively) like the one of a methyl group in a single-rotor potential. This is true, even if the coupling is much stronger than the single-rotor potential. However, the numerical value of the tunnelling splitting depends on the number of interacting methyl groups. This scenario emerges from quantum mechanical calculations for up to four coupled methyl groups. It is also supported by the preliminary results for chains of up to eight interacting methyl groups, where we use a somewhat simplified model Hamiltonian which maps the coupled rotors to a system of harmonic oscillators.