Vol.3, No.7, 617-621 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.37084
X and  -rays emission probabilities of 131I and 133Xe
Paşa Yalçın1, Arif Baştuğ2
1Department of Science Education, Faculty of Education, Erzincan University, Erzincan, Türkiye;
*Corresponding Author:
2Department of Physics, Faculty of Arts and Sciences, Aksaray University, Aksaray, Türkiye.
Received 18 May 2011; revised 4 June 2011; accepted 11 June 2011.
ABSTRACT
Radioactive nuclides as 131I and 133Xe are in-
creasingly used for both clinical diagnosis and
therapeutic treatment of the patient. For exam-
ple, 131I is used for the treatment of thyroid gland
cancer. Otherwise, 133Xe is used in ventilation
studies to assess and evaluate pulmonary func-
tion and to provide images of the lungs in both
cardiac and pulmonary diseases, such as asthma,
pulmonary emphysema, bronchiectasis, carci-
noma of the lung, and pulmonary embolism 1,2.
Furthermore, cerebral blood flow is measured
using 133Xe inhalation. In this study, the X and
 -rays emission probabilities in the decay of 131I
and 133Xe were precisely measured with a cali-
brated Si(Li) detector. Results of this study were
compared using available results in the litera-
ture. Good agreement was observed between
our results and available results in the literature.
Keyw ords: 131I; 133Xe; X-Rays Emission
Probabilities;
 -Rays Emission Probabilities
1. INTRODUCTION
Radioactive decay occurs as a consequence of the rela-
tive values of a number of basic nuclear parameters. De-
cay data are defined as those parameters relating to the
normal radioactive decay modes of a nuclide and include,
such as: half-life; total decay energies and branching frac-
tions; alpha-particle energies and emission probabilities;
beta-particle energies, emission probabilities, and transi-
tion types; electron-capture (and positron) energies, tran-
sition probabilities and transition types; gamma-ray ener-
gies, emission probabilities and internal conversion coef-
ficients; Auger and conversion-electron energies and emi-
ssion probabilities; X-ray energies and emission probabi-
lities; characteristics of spontaneous fission; delayed-neu-
tron energies and emission probabilities; delayed-proton
energies and emission probabilities3.
Beta decay is one process that unstable atoms can use
to become more stable. There are two types of beta de-
cay: beta-minus and beta-plus. During beta-minus decay,
a neutron in an atom’s nucleus turns into a proton, an
electron and an antineutrino (n  p + e– + ῡe). The elec-
tron and antineutrino fly away from the nucleus, which
shares the momentum and energy of the decay and now
has one more proton than it started with. Since an atom
gains a proton during beta-minus decay, it changes from
one element to another. For example, the radionuclides
131I (T1/2 = 8.020 d) and 133Xe (T1/2 = 5.243 d) undergo
–-decay to the excited states of 131Xe and 133Cs respec-
tively, which further de-excite by gamma emission and
the competing internal conversion process leading to
X-rays or Auger electron emission.
Physicians and physicists must know the identity and
amount of activity of each nuclide prior to administra-
tion. The possible presence of radiochemical impurities
also has to be considered, because they may compromise
the quality of the clinical results and increase the ab-
sorbed dose. Furthermore, the erroneous administration
of a low amount activity in diagnostic studies may result
in errors of diagnosis, whereas an excessively high ac-
tivity leads to an unnecessary high dose to the patient.
Both incorrect applications can delay adequate treatment,
or cause discomfort and serious damage to the patient’s
health 4.
Separately, the emission probabilities of radionuclides
with well-characterized
 - and X-rays have been used for
the efficiency calibration of X-ray and gamma-ray de-
tectors, elemental analysis, in environmental radioactive
measurements, domestic computations and activity mea-
surements 5.
In view of the above, we thought worthwhile to
measure the emission probabilities of different K and L
X-rays together with the
 -rays emitted in the decays of
131I and 133Xe using a calibrated and high resolution
semiconductor detector.
2. EXPERIMENTAL
Emission probabilities of X and  -rays following the
decay of 131I and 133Xe were measured with the experi-
mental arrangement shown in Figure 1. The
 -ray and

P. Yalçın et al. / Natural Science 3 (2011) 617-621 618
Figure 1. The experimental set-up.
X-ray intensity measurements were performed using a
Si(Li) detector with an active area of 12.5 mm2, a sensi-
tive crystal depth of 3 mm and Be window of 0.025 mm
thickness. The measured energy resolution of the detec-
tor system was 160 eV FWHM for the Mn Kα line at
5.96 keV. The energy resolution of the Si (Li) detector is
high enough to resolve of the K
 , 
and L
 , 
X-rays for
these radionuclides. The electronic set up was a standard
one consisting of a stabilized detector voltage supply
unit, FET, preamplifier, a main amplifier, an analogue to
digital converter and 1024-multichannel analyzer. The
liquid sources were housed at the center of a cylindrical
shield of 1 cm diameter and 3.4 cm length. The cylin-
drical shield consists of a glass tube covered by Mylar
film, located inside a cylindrical aluminum and lead cap
as shown Figure 1.
The experiment was carried out using 131I and 133Xe
sources in solution. The sources in a glass tube were
prepared by putting a radioactive solution containing
1,169 MBq of 131I or 4.810 MBq for 133Xe (the purity of
the 131I exceeded 98.9% and 133Xe exceeded 99.5%). The
solution for 131I contains copper sulphate pentahydrate
(CuSO4.5H2O), ammonium dihdrogen phosphate
((NH4)2HPO4), sodium chloride (NaCl), benzyl alcohol
(C6H5CH2OH) and water. Otherwise, the solution for
133Xe contains sodium chloride (NaCl) and water. In this
work, Si(Li) semiconductor detector’s efficiency was
determined by Yalçın et al. [6,7].
Two representative spectra of X and
 -rays emitted in
the decay of 131I and 133Xe are given in Figure 2. The
numbers of counts in the X and  -ray peaks of the spec-
tra were determined by fitting a convolution of a Lor-
entzian with a Gaussian. Step background functions
were applied for all peaks. Losses due to dead-time and
pile-up effects were corrected using the pulser method
8. The peak resolution, the background subtraction,
and the net peak area for both
 - and characteristic X-ray
emissions were determined using the Microcal Origin
8.0 program. In order to reduce the statistical uncertainty
in the measurement, each spectrum was recorded for
time intervals ranging from 6 to 24 h. To obtain the net
pulse height spectra of
 - and emitted X-rays, a back-
ground spectrum without the sources was stripped from
the spectrum acquired over the same time interval and
under the same experimental conditions.
3. RESULTS AND DISCUSSIONS
The emission probabilities of the principal X and
 -rays obtained from these measurements as well as pre-
viously measured and calculated values are given in Ta-
ble 1. The X and
 -ray emission probabilities were de-
termined from



ii
i
NE CE
PE EA

 (1)
where


i
NE is net count rate in the peak correspond-
ing to the energy i
E,


i
E  is detector efficiency at the
energy i
E obtained from photopeak efficiency curves
given in 6,7. A is source activity in Bq [for 131I the ac-
tivity = (1.17  0.04) MBq and 133Xe the activity = (4.81
 0.3) MBq], and


i
CE is the correction factor. The
correction factors


i
CE relating to the effects coinci-
dence summing and variations in detector geometry
were calculated using GENIE-2000 (Canberra Industries)
and the KORSUM computer programs, respectively 9.
The attenuation of the photons in the air between source
and detector due to variations of atmospheric pressure,
temperature and humidity was taken into account using
KORSUM programs.
The emission probabilities for both 131I and 133Xe are
compared with previously published values as shown in
Table 1. It is clear from Table 1 that the present experi-
mental results are in general agreement with in the lit-
erature 10-12 except for the Ll X-ray at 3.63 keV of Xe
decay product and the γ-ray at 722.91 keV for 131I.
The Cs K
 3 and Cs K  1 lines following the decay of 133Xe
strongly overlap with each other, so that these lines do
not to show up as arising separate components in the
spectrum as shown Figure 2. Therefore the total yield of
the Cs K
 3 and Cs K  1 lines is given in Table 1. Since Xe
K2 and Xe K1 lines following the decay of 131I would
be discussed, the data are given separately in the Table 1.
However, the closeness of there means that the uncer-
tainties of the calculated peak areas are high. Also, in
order to obtain good statistics, many of the counting
times were comparable with the 131I and 133Xe half lives,
so decay correction over the counting times was crucial.

P. Yalçın et al. / Natural Science 3 (2011) 617-621 619
100 1000
100
1000
10000
100000
1000000
K

=(29,461+29,782) keV

=634.726 keV

=502.193 keV

=364.689 keV

=284.651 keV

=80.284 keV
131
I
K

=33,562 keV
Counts per channel
Channal
100 1000
1
10
100
1000
10000
100000
1000000
133Xe
L(

+

)= (4.323+4.614) keV
Incoherent pike
Incoherent pike
K 

=35.811 keV
K( 

+ 

)=(30.420+31.030) keV
K( 

+ 

)=35.041 keV

=80.284 keV
Counts per channel
Channel
Figure 2. Two representative spectra of K, L X-rays and  -rays emitted obtained from a Si(Li) detector.

P. Yalçın et al. / Natural Science 3 (2011) 617-621 620
Table 1. Emission probabilities of X and  -rays following 131I and 133Xe decays.
Emission Probabilities
Measured Energy values
(keV) This Work ENSDF* Literature [12] Literature [11]
For 131I
γ-β– 80.19 ± 0.02 2.61 ± 0.06 2.62 2.63 2.60
γ-β– 284.31 ± 0.05 5.98 ± 0.01 6.14 6.20 5.40
γ-β– 364.49 ± 0.05 81.67 ± 0.04 81.70 81.60 82.00
γ-β– 503.01 ± 0.04 0.36 ± 0.04 0.36
γ-β– 642.72 ± 0.05 7.14 ± 0.02 7.17 7.12 6.80
γ-β– 722.91 ± 0.05 1.25 ± 0.05 1.77 1.78 1.60
Xe Ll 3.63 ± 0.09 0.02 ± 0.06 0.01
Xe Lα 4.11 ± 0.07 0.23 ± 0.07 0.22
Xe Kα2 29.46 ± 0.04 1.42 ± 0.08 1.40 1.37
Xe Kα1 29.78 ± 0.02 2.58 ± 0.01 2.59 2.54
Xe Kβ3 33.64 ± 0.09 0.25 ± 0.05 0.24
Xe Kβ2 34.42 ± 0.05 0.14 ± 0.05 0.14
For 133Xe
γ-β– 79.61 ± 0.03 0.27 ± 0.08 0.27
γ-β– 80.99 ± 0.01 38.20 ± 0.02 38.00
γ-β– 160.61 ± 0.08 0.06 ± 0.03 0.07
Cs Lα1 4.29±0.01 2.27 ± 0.09 2.30
Cs Lβ1 4.62 ± 0.07 1.54 ± 0.05 1.47
Cs Kα2 0.625 ± 0.03 14.35 ± 0.11 14.40
Cs Kα1 31.97 ± 0.02 26.64 ± 0.03 26.50
Cs (Kβ3 + Kβ1) 35.04 ± 0.12 4.65 ± 0.07 4.76
Cs Kβ2 35.81 ± 0.08 1.44 ± 0.07 1.48
ENSDF*: Evaluated Nuclear Structure Data File, Table of Radioactive Isotopes, Nuclide search, http://ie.lbl.gov/toi/nucSearch.asp.
As a consequence, the discrepancies between the pre-
sent measurements and previously published values of
emission probabilities are within the experimental un-
certainties.
4. CONCLUSIONS
In this paper, we have given a number of data for
photon-emission probabilities characterizing the K and L
X and
 -rays following the detail of the nuclides 131I and
133Xe. The values tabulated here can be utilized applica-
tion in the analysis of nuclear materials, in nuclear medi-
cine, determining the efficiency calibration of X and
 -ray detectors, elemental analysis, in environmental
radioactive measurements, domestic computations and
activity measurements.
We considered the self absorption of X-rays in sources
which include Cl and Cu in solution that is essential for
absorption X-ray. t is the areal mass of the sample in
g/cm2 and β is the self absorption correction factor given
by
 


 
01 2
01 2
1exp secsec
sec sec
Ki
Ki
Ki
EEt
EEt
 
 


 





(2)
where μ(E0) and μKi(E) are the attenuation coefficients
(cm2/g) of incident photons and emitted characteristic
X-rays, respectively. The angles of incident photons and
emitted X-rays with respect to the normal at the surface
of the sample θ1 and θ2 were equal to 45° in the present
setup.
Emission probabilities for K and L X and
 -rays emit-
ted in the radioactive disintegration processes were cal-
culated by using the equation 1. When we compared the
calculated K and L X and
 -rays emission probabilities
for 131I and 133Xe with the measured data, as well as with
previously published results, and an agreement within
0.8% to 4.8% was observed 10-12.
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