The optical properties of Gd

2

O

3

:Eu

3+

nanoparticles immersed in different solvent were investigated.The 4f intraconfigurational transition peaks are nearly not changed by the surrounding media.The spontaneous emission lifetime of

5

D

0

of Eu

3+

in Gd

2

O

3

nanocrystalline is significantly affected by the surrounding media

mainly due to the refractive index of the media and the filling factor of the nanocrystalline.Different models predict substantially different dependences of radiative lifetime on the surrounding media.There are some measurements intended to discriminate these models have been given

and most experimental results tend to agree with the real-cavity model.Especially

recent measurements on the radiative lifetime of Eu

3+

ion embedded in glass with varying refractive index also tend to agree with the real-cavity model in contrary to the general belief that the virtual-cavity model should be more relevant.With states of opposite parity

depends strongly on the environment and does not serve as a good examination of the real-and virtual models.To overcome the problem in 4f4f transitions

Duan and Reid analyzed the lifetimes of 5d4f transitions of Ce

3+

ions in hosts with different refractive indices and the results maintained the textbook virtual-cavity model.However

there was no intention to answer the questions why most other experimental results agree with the real-cavity model

and which model should be used for a given situation.The two models that describe the radiative lifetime:virtual cavity and real-cavity model

are with respect to "interstitial" and "substitutional" impurities

respectively.In our experiment

the real-cavity model is more reliable.