COHERENT INTERNAL AND CENTER-OF-MASS QUANTUM ROTATION OF METHYL-GROUPS IN THE P-TERT-BUTYL-CALIX[4]ARENE(2 1)P-XYLENE SUPRAMOLECULAR COMPLEX/

The low-temperature inelastic neutron scattering spectrum measured for the p-tert-butylcalix[4]arene(2: 1)p-xylene complex has been interpre ted in the framework of a quantum dynamical model assuming a rotationa l motion of the p-xylene CH3 groups correlated to the translational mo tion of their centre of mass. By comparing the experimental data with calculated energies and intensities, the effective anharmonic and anis otropic molecular potential experienced by the methyl groups has been derived. The wavefunctions deduced from the spectroscopy results are u sed to calculate the proton density distribution in the plane of the m otion.