Predicting the hyperfine structure of an EPR spectrum

We shall see In the laboratory 13.3) that radicals containing the nucleus can be used to investigate biological macromolecules and aggregates. A radical has one N nucleus (7 = 1) with hyperfine constant 1.61 mT and two equivalent protons (7 = with hyperfine constant 0.35 mT. Predict the form of the EPR spectrum. 

Strategy We consider the hyperfine structure that arises from each type of nucleus or group of equivalent nuclei in succession. So, split a fine with one nucleus, then spHt each of those lines by a second nucleus (or group of nuclei), and so on. It is best to start with the nucleus with the largest hyperfine splitting however, any choice could be made, and the order in which nuclei are considered does not affect the conclusion. 

Solution The N nucleus gives three hyperfine fines of equal intensity separated by 1.61 mT. Each fine is split into doublets of spacing 0.35 mT by the first proton, and each line of these doublets is split into doublets with the same 0.35 mT splitting (Fig. 13.42). The central fines of each split doublet coincide, so the proton splitting gives 1 2 1 triplets of internal splitting 0.35 mT. Therefore, the spectrum consists of three equivalent 1 2 1 triplets. 

---