Fig. 1.

The autocorrelation function of the total collective dipole moment 〈M_tot (0) · M_tot(t)〉 is decomposed into a rotational part Φ_D(t) [displayed with orange background] and a translational part Φ_J(t) [displayed with black background]. Because of toroidal jumps the correlation functions containing the collective translational dipole moment M_j(t) are transferred to functions involving the current J(t). Each correlation function affects the dielectric loss spectrum at different frequencies. The pure rotational 〈M_D(0) · M_D(t)〉 resides in the low frequency regime. The translational contributions from 〈J(0) · J(t)〉 are located at much higher frequencies. However, this separation in frequency space is not complete. There exists a common overlag region. The rotational-translational coupling 〈M_D(0) · J(t)〉 has more or less the same frequency range as the translational contributions.