Spectral shape of the 5D0–7F0 line of Eu3+ and Sm2+ in glass

In glass, the 5D0–7F0 line of Eu3+ is usually asymmetric in shape with a longer tail in the high-energy side, while that of Sm2+ is almost symmetric. This difference is discussed, and simulations of the line shape made by taking into account the transition mechanism and the broad distribution of the crystal-field parameter values are compared with the observed spectra. It is shown that the main cause of the different spectral shape is the difference in the dependence of the transition energy on the crystal-field parameter B20. The 5D0→7F0 fluorescence line narrows and its peak energy shows a blue shift with increasing temperature in Sm2+-doped fluoride glass. The origin of this phenomenon is also discussed.