Optical spectroscopy of CrCl63- doped Cs2NaScCl6: Broadband near-infrared luminescence and Jahn-Teller effect

Single crystals of 4.1% Cr3+ doped Cs2NaScCl6 were studied by variable temp erature optical absorption and luminescence spectroscopy. The (4)A(2g)<---- > T-4(2g) transition exhibits a great deal of fine structure both in absorp tion and emission spectra. The dynamic Txe Jahn-Teller effect in the Cr3+ T -4(2g) excited state is analyzed on the basis of the Ham quenching in the T -4(2g) spinor splitting and the vibrational fine structure in the 7 K T-4(2 g)--> (4)A(2g) luminescence spectrum. The combined effect of the a(1g) and e(g) distortions leads to a net axial compression of the CrCl63- equilibriu m geometry by 0.029 A, and an equatorial expansion by 0.088 A in the T-4(2g ) excited state relative to the (4)A(2g) ground state. These results are co mpared to those from other Cr3+ doped chloride and bromide elpasolites, and their different room temperature luminescence quantum yields are discussed on the basis of their different T-4(2g) excited state distortions. Tempera ture dependent luminescence and lifetime measurements show that in Cr3+:Cs2 NaScCl6 at room temperature the luminescence quantum yield is about 0.7. (C ) 2001 American Institute of Physics.