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The analytical expression describing dynamics of the nuclear magnetization with the use of double resonance nuclear magnetic resonance of a procedure of transfer of spin saturation under photo-induced chemical exchange is obtained. Three different experimental procedures for the definition of the effective tate constants and the quantum yield of responses ate considered.One of the numerous applications of nuclear magnetic resonance (NMR) spectroscopy is the study of photochemical reactions [1][2][3][4][5]. The use of NMR for investigating the quantum yields of irreversible photochemical reactions [1] is widely known. Besides, photochemicaUy induced dynamic polarization of nucleus allows one to examine [2, 3] the short-lived radical alternate corpuscles which appear as a result of flash photolysis of substances. Recently it was shown that with the help of dynamic NMR (DNMR), the reversible photochemical processes [6-8] can be investigated in situ. DNMR procedures on the basis of the comparison of the band shapes are promising for the study of photo-induced chemical exchange (PICE) [6][7][8]. Use of the double NMR procedures for understanding the kinetics of PICE [9] was recently offered. The goal of the present investigation is the further development of this methodical approach. For this purpose the analytical expression describing the modification of the nuclear magnetization depending on the effective rate constant of PICE at the double NMR on the basis of the ForsenHoffman procedure [10] was obtained. In the long run, this methodicat approach can be used for studying converted photochemical reactions with a characteristic 9 This work was partially presented at the Joint 29th Ampere and 13th ISMAR lntemationaI Conference on Magnetic Resonance and Related Phenomena, Berlin, 1998.

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