[Preliminary Study on the Unique Spectroscopic Characteristics of Natural and Synthetic Diamonds]

A systematic comparative study on the natural diamond, the natural diamond treated by heat or irradiation and synthetic diamond prepared by chemical vapor deposition (CVD) or High temperature and high pressure (HTHP) were carried out by UV-Vis-NIR absorption and FTIR spectra. The results showed that: natural diamond, treated natural samples such as irradiated or annealed ones under high temperature and the HTHP synthetic diamond, the reflection coefficient is obviously variation between 200 nm and 1100 nm in UV-Vis-NIR spectra of above samples. In contrast, the reflection coefficient of CVD synthetic diamond is relatively smaller than the former. Infrared spectra showed that synthetic diamonds, especially for CVD synthetic diamonds have no obvious absorption peak between 800 and 1 600 cm(-1). In additional, the results of DiamondView detection are different for different kinds of diamonds. Generally speaking, some CVD synthetic diamonds treated by HTHP appears some parallel dislocation lines, and show light-blue fluorescence. HPHT synthetic diamonds exhibit strong blocky geometrical shapes whereas some natural diamonds exhibit more tree-ring type fluorescence patterns, the color of diamonds' fluorescence image may change after treated by HTHP or irradiation. In a word, in view of the diversity and innovation of the synthesis technologies for diamond, the natural and synthetic diamonds have some similar spectra characteristic in term of UV-Vis-NIR and FTIR spectra, some special natural diamonds without typical spectra characteristic of natural ones need to be further supplemented with DiamondView, photoluminescence spectra and other instruments.