Some detailed investigations of optically detected Ē(2E) →4A2 cross relaxation in ruby
Cross relaxation betweenĒ(2E) and4A2 states of Cr3+ in ruby at an applied external magnetic field ofH=5336 Oe was measured by monitoring the ¦− 1/2〉ex→ ¦− 3/2〉g optical transition in the temperature region of 1.6 to 4.2 °K. The chromium concentration varied from 2.9· 10−4 to 4 · 10−6 Cr3+/Al3+. With a concentration greater than 2 · 10−5, the light intensity of the observed transition increases when cross relaxation takes place, while below this value it decreases. By measurement of the fluorescent intensity of one transition and simultaneously inducing EPR ground state transitions, we monitored the effect of trapping. Taking the value for trapping from fluorescence decay time measurements, we have used rate equations for calculating the actual change of excited state population when cross relaxation occurs. With this phenomenological model we are able to explain our experimental data. Finally some calculations for the effective spin temperature in theĒ(2E) state as a function of Cr3+ concentration as well as for various applied magnetic fields have been done.