Multiple interacting nuclei, hyperfine

The number of isotropic hyperfine lines from a particular nucleus depends on the nuclear spin, I, and the line multiplicity is 2/ + 1. For n equivalent nuclei, the EPR spectrum consists of 2nl + 1 lines whose relative intensities are given by binomial coefficients obtained in the expansion of (1 + x)n (Knowles et al., 1976). When nuclear hyperline interactions occur, Eq. (16.4) becomes... 

A magnetic dipole interaction between the magnetic moment of the nucleus and the internal field (intrinsic or extrinsic to the atom in origin). The result is a multiple line structure in the spectrum known as magnetic hyperfine splitting, and labelled Bht see Figure 4.45b. 

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