Measurements of the lifetime of the ruby R1 line under high pressure

The lifetime τ of the R1 fluorescence line, 2E(Ē)→4A2 of ruby (Al2O3:Cr3+) has been measured under high-pressure conditions (up to 42.7 GPa) using a modulation fluorometry technique. This study shows that τ increases linearly with pressure and that this increase is primarily caused by a rapid decrease in the transition probability of the radiative transition. The present measurements agree qualitatively with the theoretically predicted decrease in the oscillator strength at high pressure.