Abstract

Sixty-seven natural blue diamonds, including the two largestsuch gemstones known (the Hope and the Blue Heart), were probedby ultraviolet radiation, and their luminescence was analyzedusing a novel spectrometer system. Prior to this study, thefiery red phosphorescence of the Hope Diamond was regarded asquite rare compared to greenish-blue phosphorescence. However,our results demonstrated that virtually all blue diamonds phosphoresceat 660 nm (orange-red) but that this emission often is obscuredby a concomitant luminescence at 500 nm (green-blue). Althoughboth bands were nearly always present, the relative intensitiesof these emissions and their decay kinetics varied dramatically.Consequently, phosphorescence analysis provides a method todiscriminate among individual blue diamonds. Treated and syntheticblue diamonds showed behavior distinct from natural stones.Temperature-dependent phosphorescence revealed that the 660nm emission has an activation energy of 0.4 eV, close to the0.37 eV acceptor energy for boron, suggesting that the phosphorescenceis caused by donor-acceptor pair recombination.