Temperature dependence of fluorescence yield and lifetime ofF+centers in SrO

The excited states of the $F^{+}$ center in neutron- or proton-irradiated SrO have been studied by measuring the temperature dependence of the yield and lifetime of the $F^{+}$ fluorescence over the temperature range from 5 to 140 K. Both the fluorescence yield and lifetime decrease in two stages; one over the temperature range from 5 to 60 K, and the other over the range 60 to 140 K. The results are interpreted in terms of a three-level model of the $F^{+}$ center which is suggested by recent theoretical work. The lowest radiative level, which has a lifetime of 0.42 μsec, is found to be 0.05 eV below the conduction band. Another level is found only 0.005 eV above this radiative level. In order to account for the results, nonradiative decay to the ground state appears to occur from this second level.