FULL MATRIX ANALYSIS OF CROSS-RELAXATION FAILS IN FRACTIONALLY DEUTERATED MOLECULES

We have analyzed cross-relaxation in fractionally deuterated molecules and showed that the full matrix analysis fails except when the diluti on is extreme. This is because the isotopic dilution alters the matrix exponential relationship between the observed spectrum and the cross- relaxation rate constants sought. Consequently, an average of the spec tra of various isotopomers differs from the matrix exponential of an a verage relaxation matrix. We have derived a series expansion that allo ws the determination of the cross-relaxation rate constants in arbitra rily deuterated molecules.