RUBY AT HIGH-PRESSURE .3. A PUMPING SCHEME FOR THE R-LINES UP TO 230 GPA

We report on a B-line pumping scheme for exciting ruby R-line fluorescence which becomes useful above approximately 100 GPa (100 GPa = 1 Mbar). We have measured five ruby fluorescence lines in a quasihydrostatic-hydrogen-pressure medium to 230 GPa by using the most efficient argon-ion pump-laser wavelength at each pressure. The frequencies of the R and R' lines, as determined in the cubic-crystal-field approximation, shift linearly with the fractional volume change to the highest pressure reached. The R1 and the R3' lines remain thermalized and the oscillator strength of the R3' line increases relative to the R1 line to 230 GPa.