Fluorescence Colors from Different Defect Centers. 3D fluorescence spectra provide an excellent opportunity to examine fluorescence produced by individual defects as well as the contributions of multiple defects. By directly depicting the relationship between UV excitation and fluorescence emission, these spectra illustrate the emission resulting from the various optical centers. Fluorescence spectra from diamonds dominated by individual color centers are relatively simple and consistent, as discussed for each defect in the Results section.
In most diamonds, multiple defect centers occur together. Even under pure 365 nm LWUV excitation, the fluorescence color will be a mixture of the fluorescence from different defect centers. The fluorescence may also have uneven zoning due to defect distributions. Visual observation alone is not an adequate basis for interpreting a diamond’s fluorescence color with respect to the corresponding defect centers. The energy of the excitation source can have a profound effect on the resulting fluorescence color and luminescence spectra, and it must be carefully considered.