ion decays in the nanosecond range (?30 ns), whereas in the
terbium ion it decays in the millisecond range. In [18] lifetime
measurements of the Ce 3þ emission glasses were performed
monitoring at 470 nm, after 337 nm pulsed laser excitation within
the Ce 3þ 4f-5d absorption transition. The cerium emission decay
follows a single-exponential decay with a lifetime value of
6572 ns. This very short decay time agrees with the electric
dipole allowed nature of the Ce 3þ 4f-5d transition. Lifetime
measurements of the 5D3 and
5 D 4
levels of Tb 3þ in zinc–sodium–
aluminosilicate glasses doped Ce 3þ /Tb 3þ were performed mon-
itoring the
5 D 3 - 7 F 4
(435 nm) and
5 D 4 - 7 F 5
(550 nm) emissions
with Ce 3þ excitation at 320 nm. The decay curves of these
emissions are non-exponential. The effective decay times of the
5 D 3
and
5 D 4
states are 2.570.2 ms and 4.170.3 ms, respectively.
The long decay time of the terbium emissions is typical for the f–f
transitions originating from
5 D 3
and
5 D 4
states. Our results show
that for in all the samples the decay kinetics of the luminescence
band at 436 nm (Fig. 6) a cannot be described by the monoexpo-
nential decay kinetics, and the kinetics can be divided into two
stages: the fast stage of decay with the relaxation time τ fast
?2372 ms and the slow component τ slow ?14074 ms. As the
concentration of cerium changes, the duration of both fast and
slow stages changes insignificantly (Fig. 6 a, inset). This means that
the processes of excitation and relaxation of the
5 D 3
level are
apparently not related directly to the presence of cerium ions in
the glass host