High-pressure physics: the 1-megabar mark on the ruby r1 static pressure scale

Ruby crystals were subjected to a static pressure greater than 1 megabar in a diamond-windowed pressure cell. The pressure was monitored continuously by observing the spectral shift of the sharp fluorescent R(1) ruby line excited with a cadmium-helium gas-diffusion laser beam. One megabar appears to be the highest pressure ever reported for a static experiment in which an internal calibration was employed.