3. Results and discussion
The replacing H2O by D2O in lanthanide sulfate crystallohydrates
did not change the positions of the maxima in PL spectra.
A crystal structure of terbium sulfate crystallohydrate with heavy
water (Fig. 1) and that with normal one [18] was identical. The
intense band of the OD group at 2300–2500 cm1 in IR spectrum
clearly indicates the replacement of normal crystallized water by
the heavy one.
Comparing the deuterated and non-deuterated crystals (Fig. 2)
clearly indicates an increase in photoluminescence intensity.
To compare correctly total luminescence intensity in the
deuterated and non-deuterated samples, we calculated the area
of the maxima in the spectra. For a single maximum, the normal
or the Gaussian distribution can be used:
IðkÞ ¼ Imin þ Imax exp k kImax
ð Þ2
2r2
!
ð1Þ
where Imin is the average intensity when luminescence is absent in
the minimum point of spectrum (noise), Imax is the intensity of peak
maximum in spectrum, kImax is the wavelength at the maximum
intensity; r is calculated as follows:
r ¼ 1
2
DkffiffiIffimffiffiaffiffixffi
ln 4
p
ð2Þ
where DkImax is a width at the half-maximum.
The luminescence spectrum consisting of several peaks is represented
as a superposition of all peaks:
IðkÞ ¼ Imin þ
Xn
i¼1
Imaxi exp k kImaxi
2
2r2i
!
ð3Þ
To compare the luminescence intensities, we calculated the
ratio of the total integral luminescence intensities of the deuterated
and normal crystallohydrates:
SID2O
SIH2O
¼
R
ID2OðkÞdk R
IH2OðkÞdk
ð4Þ
These values are given in Table 1.
The decay curves of luminescence intensity at the pulsed photoexcitation,
that inserted in Fig. 2, are well described by a simple
exponential function:
I ¼ I0 exp t
s
ð5Þ