INFRARED-ABSORPTION BY THE SINGLE NITROGEN AND A DEFECT CENTERS IN DIAMOND

The infrared absorption spectra of a suite of twenty-one type lb synth etic diamonds have been recorded, and the concentrations of nitrogen i n the form of single substitutional N atoms in these specimens determi ned by electron spin resonance measurements. It is found that an absor ption coefficient, at 1130 wavenumbers, of 1 cm-1 is produced by 25.0/-2 at.p.p.m. of nitrogen in this form, a result identical to that of Chrenko, Strong and Tuft and consistent also with that of Woods, van W yk and Collins. Seventeen of these specimens were heated at temperatur es between 1800 and 2050-degrees-C, under a stabilizing pressure, to b ring about an appreciable degree of aggregation of the single N defect s into A centres, or nitrogen pairs. For each specimen the residual, u naggregated single N defect concentration was then determined by elect ron spin resonance. The difference between this and the original value gave the concentration of nitrogen in the form of A defects. The infr ared absorption strength of the A centres was obtained in each case by decomposition of the infrared spect-rum into the residual single N, a nd A, components. In this way it is found that the absorption coeffici ent at 1282 wavenumbers due to A centres is 1 cm-1 per 16.2 +/- 1 at. p.p.m. This value is in good agreement with an earlier result obtained by inert-gas fusion and the result given in the paper that immediatel y follows.