Nuclear magnetic relaxation induced by chemical exchange

Abstract

A new method of treating chemical exchange in nuclear magnetic relaxation theory is proposed. The essence of the method is to introduce the exchange in the spin hamiltonian by writing , where f_i (t) is a function of time and has the value unity if the nucleus considered is at site i at time t, and zero otherwise. The method is applied to cases where the chemical exchange is faster than the relaxation. Some previously derived results are re-derived and in some cases made more general. The case of very fast intramolecular exchange is also considered.