The radiative transition probability is a fundamental property for an optical transition. Extensive study on theoretical and experimental research has been conducted to relate the photonic environment around the emitter with electric dipole (ED) transition probabilities . Nanocrystals (NCs) doped with luminescent ions are ideal as probes to test theoretical models. Recent work has established that the NC-cavity model accurately describes the influence of the refractive index n of surrounding medium on ED transition rates .
For magnetic dipole (MD) transitions theory predicts a simple n3 dependence of the MD transition rates. However, experimental evidence is difficult to obtain . In the current study, we use hydrophobic Eu3+-doped core-shell NCs suspended in apolar solvents with different refractive index n. The ratio between the ED and MD transition rates and the total transition rate is in excellent agreement with the NC-cavity model for ED transitions and the simple n3 dependence for MD transitions. Moreover, Gd3+-doped core-shell NCs, whose 6P7/2-8S7/2 emission is of exclusive MD transition, are employed to see more insight. Thus our study provides the experimental evidence for the theoretically predicted n3 dependence for MD transition rates.
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