Elimination of pressure-induced fluorescence in diamond anvils

At pressures above one megabar (100 GPa) in high-pressure diamond anvil cell experiments the ruby fluorescence signal needed for pressure calibration is increasingly difficult to measure. A primary cause of this difficulty is the presence of an intense pressure-induced diamond fluorescence. We give a tentative identification of this pressure-induced fluorescence and report on a technique for the elimination of this fluorescence. We demonstrate that weak ruby signals, completely hidden by diamond fluorescence, are now easily measured with our technique.