Study of local concentration of single substitutional nitrogen atoms in microdiamonds from the Kokchetav massif

In this communication we present an estimation of the concentration of single substitutional nitrogen atoms (P1 centre) from EPR data in Kokchetav diamonds. We first performed an analysis of local PI centre concentrations using van Wyk's treatment (van Wyk et al., 1997) of the line width of the resolved EPR spectrum. Also by analysing the dependence of the line-width of the broad exchange line on the PI concentration in range higher than 1000 ppm in synthetic diamonds, we obtained a calibration curve allowing the estimation of the local P1 centre concentration higher than 1000 ppm and the local volumes occupied by substitutional nitrogen atoms without taking measurements of microcrystalline volume. In addition to the development of a method for calculating high local nitrogen concentrations, the aggregation process in PT-treated Kokchetav diamonds has been given considerable attention and it was shown that the rate of nitrogen aggregation in these diamonds is consistent with data given in Evans (Evans & Qi, 1982).