Absorption, excitation and photoluminescence spectra
The optical transmission spectra of glasses are shown in Fig. 1.
Increase in the concentration of cerium ions leads to a slight red-
associated with f–f transitions in the terbium ion [7]. The trans-
mission coefficient at 350 nm is ?70%. The absorption peak at
It is well established that the transitions from the lowest 5d-
levels in Ce 3þ ions to the Ce: 2 F 5/2 and Ce: 2 F 7/2 levels of the ground
configuration split by the spin–orbit interaction are responsible for
the emission of cerium ions [14,15]. The PL spectra for glass
samples with different concentrations of cerium are shown in
Fig. 2. As it was reported in [15], the study of fluoride crystals with
good transmittance in the ultraviolet region showed that the
luminescence spectrum is characterized by 315–330 nm bands
( 2 F 5/2 and
2 F 7/2
transitions, respectively). The observed distorted
intrinsic absorption spectrum of the emission of cerium ions is due
to sufficiently high absorption of the glass matrix in the UV region
(Fig. 2). The overlap of the absorption and luminescence spectra
can contribute to reabsorption of the shortwave cerium emission
by dopant ions.