Calibration of the ruby pressure scale to 150 GPa

For many years the ruby pressure standard has been the so-called quasi-hydrostatic scale of Mao, Xu, and Bell published in 1986. The calibration was determined by X-ray diffraction of metal markers in an argon pressurization medium to 80 GPa, along with simultaneous measurement of the shift of the ruby R lines. We have used data in the literature, as well as our own, mostly for ruby in quasi-hydrostatic helium, to produce a new ruby scale with calibration data that extends to 150 GPa. The new scale shows that at the highest shifts of the ruby R lines the pressures are substantially higher than on the old scale. To understand small systematic shifts of the pressures as determined from the X-ray diffraction of metal markers used in the calibration, a finite element analysis of quasi-hydrostatic conditions in a diamond anvil cell has been carried out. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.