NMR spin echoes for molecular rotators with C-3 symmetry

NMR spin echoes are calculated for a rotator consisting of three spin-1/2 n uclei whose three-particle wave function obeys C-3 symmetry. On decomposing the nuclear dipole-dipole interactions in terms of irreducible operators o f the representations of the group C-3 it is found that for spins belonging to the A-representation, the echo amplitude is maximized for a pi/2-pi/3 R F pulse sequence. The dependences of the echo formation on the orientation of the rotor and on the strengths of the dipolar interactions and the magne tic field inhomogeneities are discussed. (C) 2000 Academic Press.