Electron-spin resonance lines, relative intensities

In Fig. 4.15.1 we reproduce the electron spin resonance spectrum of monoprotonated / -benzosemiquinone in tetrahydrofuran at — 63°C, a spectrum which shows most of the features discussed above. The spectrum has been analysed in terms of four hyperfine splitting constants, as shown in Fig. 4.15.1, since the asymmetric disposition of the —OH group causes the protons meta to the site of protonation to be non-equivalent. The four splitting constants are readily obtained by measuring distances from the first line of the spectrum the g-value may of course be obtained by simultaneous measurement of microwave frequency and magnetic field at the centre of the spectrum. Readers unfamiliar with line-width effects may care to compute the expected relative intensities of the lines and compare the results with the experimental amplitudes of the first derivative trace. In such a presentation the peak-to-peak amplitude, for a Lorentzian line, is proportional to the reciprocal of the square... 

More sensitive ESR measurements over a wider magnetic field range find additional resonances in phosphorus- and arsenic-doped material, examples of which are shown in Fig. 5.11. The extra lines (two for phosphorus and four for arsenic) are due to the hyperfine interaction of the electron bound to the donor (Stutzmann and Street 1985). The ESR spectra have exactly the number of lines and relative intensities expected from the nuclear spins of and for phosphorus and arsenic atoms. The splitting of the lines, is proportional to the electron density at the nucleus and is a measure of the localization length, r, of the donor. 

---