Measurement of transverse relaxation in coupled spin systems by semi-selective refocusing: evidence for interference of CSA and dipolar relaxation

A novel spin-echo expt. is proposed that uses semiselective Gaussian pulse cascades for refocusing in systems with homonuclear couplings. The expt. allows one to obtain evdience of differential T2 effects due to cross-correlation of proton chem. shift anisotropy and proton-proton dipolar interactions in a small arom. compd. at 9.4 T. The spin-echo expt. was applied to measure transverse relaxation rates for selected multiplets of the cyclic undecapeptide cyclosporin. Possible extensions to multiple-quantum spin echo-spectroscopy are indicated. [on SciFinder (R)