A density matrix formulation is used to investigate the transient NMR effects which occur when the rf fieldH1is changed discontinuously for a coupled AB system undergoing intramolecular chemical exchange. It is shown that the problem reduces to the solution of two matrix differential equations. Explicit solutions are obtained and discussed for two special cases: (i)H1thinsp;equals;thinsp;0fortthinsp;thinsp;0, H1thinsp;equals;thinsp;weak observing field fortthinsp;thinsp;0; and (ii)H1thinsp;equals;thinsp;infin;fortthinsp;thinsp;0, H1thinsp;equals;thinsp;weak observing field fortthinsp;thinsp;0. For Case (I) it is shown that the Andersonndash;Weiss theory gives the same results. Also, our formulation is used to determine the conditions under which the absorption intensity can be calculated by assuming it to be proportional to thezcomponent of the corresponding nuclear magnetization. Finally, the effect of inhomogeneities in the static fieldH0is treated briefly. For a Lorentzian distribution of inhomogeneities, it is shown that the transient as well as steadyhyphen;state broadening effects can be accounted for by replacing the linewidth parameterlpar;1thinsp;sol;thinsp;T2rpar;withlpar;1thinsp;sol;thinsp;T20rpar;thinsp;plus;thinsp;lpar;1thinsp;sol;thinsp;T2*rpar;, wherelpar;1thinsp;sol;thinsp;T2*rpar;gives the width of the inhomogeneity function.
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