An automated technique for detailed μ-FTIR mapping of diamond and spectral deconvolution

Since the original classification of diamonds based upon their absorption in the one-phonon region of the mid-infrared (IR) range was first introduced, a vast amount of research has been carried out in this field. The result today is that IR analysis has become the principle tool for classifying diamonds based upon the concentration and aggregation state of nitrogen, the most common impurity found within their crystal lattice. These studies have shown that diamonds can contain a large range of nitrogen, from nominally nitrogen free i.e. below detection limits (termed Type II) to nitrogen rich (termed Type I) with up to 5000 ppm. It has also been shown that the nitrogen concentration, aggregation and distribution in an individual stone can be either homogeneous or heterogeneous.