S-T0-type CIDNP

CIDNP arises through the interplay of three processes (see labels 0- in Chart I), the third of which is only necessary in the case of S T0-type CIDNP. 

Figure 5. Explanation of an S- T0-type CIDNP net effect with vector models (left), resulting schematic population diagram (center), and NMR spectrum (right). The example describes a radical pair with one proton in radical 1, triplet precursor, product of the singlet exit channel, gq > g2, and positive hyperfine coupling constant. For the vector models, a clockwise sense of precession has been chosen, the labels 1 and 2 designate the radical and a> and /i) the nuclear spin state, and the dotted vertical lines in the projections give the amount of singlet character. For further details, see the text.

Figure 9. Calculated relative CIDNP intensities (in a.u.) of S T0-type CIDNP generated in the photolysis of phenylsubstituted (in the a position) 1 versus dimensionsless rates of spin-orbit coupling and scavenging. For further explanation, see the text. [Adapted from K. C. Hwang, N. J. Turro, and C. Doubleday, J. Am. Chem. Soc., 113, 35 (1991), with permission. Copyright 1991 American Chemical Society.]...

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