Dynamics and energy transfer of Sm2+ in KY3F10 crystals

Three distinct Sm2+ centers in KY3F10 have been identified by laser selective excitation. The excited states of two of the Sm2+ centers consist of the D-5(J) (J = 0,1,2,3) multiplets and high lying 4f(5)5d states, whereas the bottom of the 4f(5)5d states for the third Sm2+ center lies just above the D-5(0) nmItiplet. Vacuum ultraviolet (VUV) and ultraviolet (UV) excitation, corresponding to the 4f -> 5d transitions, produce cascade luminescence from the D-5(J) (J = 0,1,2,3) excited multiplets to the lowest F-7(J) (J = 0,1,2,3,4) multiplets. UV excitation also produces a broad emission band with a peak at 450 nm, which may be assigned to color centers (F center) being an electron trapped at a F- vacancy as a charge compensator for Sm2+. The temperature dependence of the Sm2+ luminescence spectra excited by VUV and UV radiation clearly demonstrates inter-configurational relaxation from the 4f(5)5d excited states to the D-5(J) (J = 0,1,2,3) multiplets and intra-configurational relaxation from the D-5(3) multiplet to the D-5(J) (J = 0,1,2) multiplets. The luminescence decay curves also show energy transfer between the two Sm2+ centers.