Electronic Spectra of Cs2NaYbF6and Crystal Field Analyses of YbX63-(X F, Cl, Br).

Detailed analysis of the vibronic structure in the electronic absorption spectrum of Cs2NaYbF6at temperatures between 10 and 300 K enables the crystal field energy level diagram of Yb3in this cubic host to be deduced. Ultraviolet and visible laser excitation of Cs2NaYbF6, Cs2NaY0.9Yb0.1F6, and Cs2NaHo0.99Yb0.01F6give spectral features mainly due to Yb3being situated at a range of defect sites. The 4f13crystal field analyses of octahedral YbX63-(X F, Cl, Br) systems show the expected trends in parameter values, but the energy level fits are poor. Inclusion of the interaction with the charge-transfer configuration 4f14np5provides an exact fitting of energy levels for YbX63-, and a smooth variation of ff and fp crystal field parameters for Cs2NaLnCl6(Ln Er, Tm, Yb) is observed. [ABSTRACT FROM AUTHOR]