Refinement of the ruby luminescence pressure scale

A comparison of recent high pressure x-ray diffraction data for diamond and Ta with low pressure ultrasonic data provides a basis for the refinement of the ruby luminescence pressure scale, whereby not only the slope and curvature parameters A=1904 GPa and B=7.665 of the previous scale are changed, but evidence is given for a modified form for the ruby R1 luminescence line shift under pressure with A=1820 GPa, B=14, and an additional parameter C=7.3. This revised ruby pressure scale resolves to a large extent previous discrepancies between equation of state data derived from x-ray measurements on the basis of the currently used ruby scale, on the one hand, and ultrasonic or theoretical studies, on the other hand.