Excitation of ruby fluorescence at multimegabar pressures

We demonstrate the excitation of strong ruby fluorescence at multimegabar pressures by red incident radiation. We have studied the ruby R1 and N2 lines to 251 GPa and measured the R1 line intensity as a function of pump wavelength. This new method of exciting ruby fluorescence enables easy pressure determination at pressures beyond the 250 GPa limit previously predicted by Ruoff.