RESONANT AND PHONON-ASSISTED EXCITATION-ENERGY TRANSFER IN THE R(1) LINE OF [CR(OX)(3)](3-)

In resonant fluorescence line narrowing (FLN) experiments in the R(1) transition of the [Cr(ox)(3)](3-) chromophore in [Ru(bpy)(3)][NaAl:Cr( 1%)(ox)(3)] and [Rh(bpy)(3)][NaCr(ox)(3)]ClO4 multiline spectra are ob served at 1.8 K, (ox=oxalate, bpy=2,2'-bipyridine). For [Rh(bpy)(3)][N aCr(ox)(3)]ClO4 the number of lines and their relative intensities dep end critically upon the excitation wavelength within the inhomogeneous distribution, and in time-resolved FLN experiments additionally upon the delay. This behavior is clear evidence for a resonant energy-trans fer process. At 4.2 K the more common phonon-assisted process becomes dominant, manifesting itself as spectral diffusion.