The imaginary part of the magnetic dipole-dipole cross correlation spe
ctral density in spin 1/2 systems generates a novel type of three-spin
Hamiltonian with terms IizIjzIkz, IizIjxIkx and IizIjyIky and permuta
tions in the spin labels i, j, k. These terms cause asymmetric positio
ns of the spin multiplet components, which could not be explained by s
calar J-coupling and chemical shift terms. (C) 1996 American Institute
of Physics.