On the rotational spectra of endohedral atoms at fullerenes: the off-centre case

A simple Hamiltonian describing the rotational dynamics of endohedral off-center atoms at fullerenes is reported. Using this Hamiltonian rotational spectra for Li+@C60 are calculated and the effect of the angular dependence of the atom-cage potential energy on such spectra is evaluated. Complexity, large density of transitions and the appearance of rotational oscillations and librational bands are the main features of the calculated spectra.