Light Sources. In 2005, researchers studied the phosphorescence spectra of the Hope diamond
using a CCD spectrometer and a broadband UV source that provided radiation in the 215–400 nm range. This broad range made it impossible at the time to distinguish the various phosphorescence reactions at short- and long-UV wavelengths unless a filter that limited the wave-length range was used. This considerably reduced the luminescence signal intensity and required a high-sensitivity, low-resolution spectrometer.