“…Because the inhomogeneous linewidth Fin h = 3.8 cm-1 (FWHM) is larger than the zero-field splitting of the #A 2 ground state /9 = 1.3 era-~ and the homogeneous iinewidth Fho m = 0.012 cm -I (FWHM) [7], a threeline pattern would be expected in the FLN spectrum, with sidebands at +D from the resonant line [1]. Three-line patterns have been observed in a number of Cr 3+ systems where luminescence occurs from the 2E state, such as A1203:Cr 3+ [8][9][10] The inhomogeneous distribution of transition energies is given by a Gaussian. As is normal in an FLN experiment with two inhomogeneously broadened and overlapping transitions, two sets of molecules are excited when irradiating at a given laser frequency ~ within the inhomogeneous envelope: a set denoted i = 0, for which the transition ga ~ e is resonant (~a0 = ~t), and a set denoted i + 1 = 1, for which the transition gb ~ e is resonant (~bl = ~t)" Resonant energy transfer is possible within these subsets individually.…”