Effects of higher rank multipoles on relaxation of an I=3 spin system

Magnetic multipoles of rank higher than one become active in spin systems w ith I > 1/2 and their contribution to relaxation depends on dynamics. The a ppearance of multipole terms complicates the relaxation description and sup ports the multiexponential behavior of relaxation. In this paper the effect s of high-rank multipoles on lineshape and longitudinal relaxation of I = 3 spin systems are presented. Results obtained from both numerical simulatio n and experimental data show that longitudinal and transverse relaxation ar e strongly influenced by these multipole terms, especially at lower tempera ture where, due to lower molecular mobility, the extreme narrowing conditio n is not fulfilled. (C) 2001 Academic Press.