MEASUREMENT OF RELAXATION-TIMES OF PARAMAGNETIC IONS IN CRYSTALS: RUBY.
JOHNS HOPKINS UNIV BALTIMORE MD CARLYLE BARTON LAB
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Experimental methods of measuring relaxation times radiative and non-radiative of the excited states of paramagnetic ions in crystals are described. In particular, various methods of excitation and detection of fluorescence radiation, when short lifetimes andor weak fluorescence are involved, are discussed in some detail. Explicit solutions of the rate equations for a simple 3-level system are obtained in order to clarify the effects of the shape of the fluorescence excitation pulse on the fluorescence radiation which is observed. The fluorescence lifetimes of the R-lines of ruby have been measured at 77K and 297K over a wide range of Cr3 concentrations 0.004 to 2.5. On the assumption that the variation of R-line lifetime with temperature in standard ruby laser rods is the major factor which decreases the threshold efficiency for laser action with increasing temperature, these results would indicate the possibility of quasi-continuous laser action for a ruby rod with a Cr3 concentration of the order of 0.002. Author