Electron spin resonance in electron-irradiated diamond

The room temperature electron spin resonance spectrum of type IIa diamonds irradiated with 2 Mev electrons has been measured at a frequency of 9.5 kMc/s. The spectrum has been analysed into four systems, all of which show a g value within 0.2% of the free-spin value: A single isotropic line with a width of about 5 gauss. An anisotropic system of up to 24 lines of width about 5 gauss with a maximum splitting of ±1.5 kgauss and symmetry axes near to the 〈221〉 directions. An anisotropic system of up to 6 lines of width 25–50 gauss with a maximum splitting of ±1.5 kgauss and symmetry axes along the 〈100〉 directions. A broad absorption with a complicated anisotropic structure, showing a maximum splitting of ± 150 gauss. It is suggested that the centres giving rise to the (b) and (c) systems consist of two localized components, and that the splitting arises from magnetic dipolar interaction between them. The geometry of the axes can be explained if it is assumed that one of the components is a double defect such as a di-interstitial with the spin acting as if localized at its centre. System (d) is interpreted as arising from vacancy-interstitial pairs of various separations and orientations.