Photoacoustic spectroscopy study on the co-luminescence phenomena of solid rare earth complexes

Photoacoustic (PA) spectra of coprecipitates Tb3+-Ln3+-Sal complexes are reported (Sal: salicylic acid; Ln3+:Gd3+ or Nd3+). For Tb3+-Gd3+-Sal coprecipitates, the PA intensity in the region of ligand absorption decreases firstly with increasing the concentration of Gd3+, and then increases. For Tb3+-Nd3+-Sal coprecipitates, the PA intensity of the ligand increases remarkably. The difference in PA intensities is interpreted in terms of probability of nonradiative transitions. The changes of luminescence spectra turn out to be complementary to the PA spectra. Combined with PA phase shifts, which are directly related to the relaxation processes, the luminescence enhancement and quenching phenomena of the coprecipitates are discussed by two aspects: radiative and nonradiative processes.