One-phonon infrared absorption in diamond

The defect-induced one-phonon infrared absorption in natural diamond can be divided into a number of overlapping components. The computational method of extracting the spectral shapes of these contributions is described. The A and B components are associated with nitrogen defects. The A defect is a pair of substitutional nitrogen atoms and the B defect is currently considered to be an agglomerate containing four nitrogen atoms. The C spectrum is associated with the singly substituted nitrogen atom and is characteristic of synthetic diamonds. The D spectrum has been observed only in diamonds which also contain B defects, and for this reason is also considered to be a defect which contains nitrogen. Some studies have been carried out on the thermal stability of the A, B and D defects during heat treatment in the range 2100-2800 degrees C under a pressure of 9.5 GPa. A possible nitrogen aggregation sequence is suggested to describe the observations.