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 D-5(0)-F-7(0) transition at 10 K. Line-narrowing fluorescence of the D-5(0)-->F-7(1) 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 D-5(0)-F-7(0) 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 ki,oh-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. (C) 1997 American Institute of Physics.