Two-photon excitation spectroscopy of 4f(7)-> 4f(7) transitions of Eu2+ ions doped in a KMgF3 crystal

Intraconfiguration 4f(7) --> 4f(7) transitions of Eu2+ in KMgF3 have been i nvestigated by two-photon excitation (TPE) spectroscopy at 10 K. Emission b ands due to the P-6(7/2) --> S-8(7/2) and I-6(7/2) --> S-8(7/2) transitions are obtained by two-photon excitation into the I-6(J) (J=7/2,9/2,17/2,11/2 ,15/2,13/2) and D-6(J) (J=1/2,7/2,3/2,5/2) states. The TPE spectrum of the I-6(7/2) --> S-8(7/2) emission is observed to be different from that of the P-6(7/2) --> S-8(7/2) emission. This is explained by the relative position s of the lowest crystal-field component of the I-6(7/2) level and the lowes t level of the 4f(6)5d configuration for cubic-site and non-cubic-site EU2 ions. The observed TPE spectra are satisfactorily interpreted by a suggest ion that the I-6(7/2) --> S-8(7/2) emission is produced by only cubic-site Eu2+, while the P-6(7/2) --> S-8(7/2) emission is produced by both cubic-si te Eu2+ and non-cubic-site EU2+.