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 $\text{A=1904\hspace{0.17em}}\mathrm{GPa}$ and $\text{B=7.665}$ of the previous scale are changed, but evidence is given for a modified form for the ruby $R_1$ luminescence line shift under pressure with $\text{A=1820\hspace{0.17em}}\mathrm{GPa},$ $\text{B=14,}$ and an additional parameter $\text{C=7.3.}$ 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.