Fluorescence line narrowing spectroscopy of Sm2+ and Eu3+ in sodium borate glasses

A fluorescence line narrowing technique was carried out for sodium borate glasses containing a Sm2+ ion and its isoelectonic Eu3+ ion under a pulsed tunable dye laser excitation. In order to obtain site-dependent information, measurements were made by exciting the inhomogeneously broadened D05-F07 transition at 10 K. Line-narrowing fluorescence of the D05→F17 transition and the temporal changes of the emission lines were investigated as a function of excitation energy, and the dynamics of excited states for both ions were compared with each other. The results indicate that the site-to-site variations of the inhomogeneous broadening of D05-F07 transitions are attributed to the apparent difference in local environment between the Sm2+ and Eu3+ ions doped in borate glasses with Na2O content from 10 to 20 mol %. Also, a decrease in concentration of rare-earth ions causes a more significant effect on Eu3+ ions than on Sm2+ ions in the high-excitation-energy range. It is concluded that the difference in the local environment between Sm2+ and Eu3+ is mainly ascribable to the difference in the valence and in the ionic radius.