Optical characterization of natural Argyle diamonds

Optical centers in natural diamonds from the Argyle mine have been characterized by absorption and photoluminescence techniques. Many of those diamonds show characteristic PL spectra with a large number of slowly decaying centers, most of which can be attributed to the Ni impurity. A linear correlation was observed between the intensity of the 3107 cm(-1) hydrogen-related peak and the concentration of IR-active nitrogen. It may be accounted for by the presence of NH3, NH4 and N-2 gases as sources of nitrogen during diamond growth. It is shown that the unique blue-gray color of some Argyle diamonds is determined not only by the high hydrogen content, but also a small concentration of tri-nitrogen complexes in combination with a large concentration of two- and four-nitrogen defects. (C) 2002 Elsevier Science B.V. All rights reserved.