We report laser excited fluorescence in high purity synthetic diamond
anvil to pressures of 370 GPa in a diamond anvil cell device. The nitr
ogen impurity level in this diamond is extremely low, and it allows us
to study the stress effects on the optical transitions in diamond wit
hout interference from impurities. Pressure in the diamond anvil cell
was measured by x-ray diffraction using the platinum standard. Pressur
e dependence of the fluorescence peak was measured between 270 and 370
GPa in the visible spectral range. The variation of excitation laser
wavelength shows clear cutoff in the excitation threshold in the 514-6
33 nm range at 370 GPa. (C) 1996 America Institute of Physics.