4f8–4f8 Ultraviolet absorption spectrum of Cs2NaTbCl6

The ultraviolet absorption spectrum of a crystal of Cs2NaTbCl6 has been recorded at 15 and 35 K. Spectral features have been assigned to magnetic dipole zero phonon lines and TbCl 6 3 - moiety mode vibronic structure. A comparison is made of the derived electronic energy level scheme with that from two-photon excitation experiments and the agreement is good. The differences in spectral selection rules for these two approaches are highlighted.