X and-rays emission probabilities of 131 I and 133 Xe

Radioactive nuclides as I and Xe are increasingly used for both clinical diagnosis and therapeutic treatment of the patient. For example, I is used for the treatment of thyroid gland cancer. Otherwise, Xe is used in ventilation studies to assess and evaluate pulmonary function and to provide images of the lungs in both cardiac and pulmonary diseases, such as asthma, pulmonary emphysema, bronchiectasis, carcinoma of the lung, and pulmonary embolism 1,2. Furthermore, cerebral blood flow is measured using Xe inhalation. In this study, the X and -rays emission probabilities in the decay of I and Xe were precisely measured with a calibrated Si(Li) detector. Results of this study were compared using available results in the literature. Good agreement was observed between our results and available results in the literature.


INTRODUCTION
Radioactive decay occurs as a consequence of the relative values of a number of basic nuclear parameters.Decay 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 fractions; alpha-particle energies and emission probabilities; beta-particle energies, emission probabilities, and transition types; electron-capture (and positron) energies, transition probabilities and transition types; gamma-ray energies, emission probabilities and internal conversion coefficients; Auger and conversion-electron energies and emission probabilities; X-ray energies and emission probabilities; characteristics of spontaneous fission; delayed-neutron 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 -+ ῡ e ).The electron 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 131 I (T 1/2 = 8.020 d) and 133 Xe (T 1/2 = 5.243 d) undergo  --decay to the excited states of 131 Xe and 133 Cs respectively, 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 administration.The possible presence of radiochemical impurities also has to be considered, because they may compromise the quality of the clinical results and increase the absorbed dose.Furthermore, the erroneous administration of a low amount activity in diagnostic studies may result in errors of diagnosis, whereas an excessively high activity 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 detectors, elemental analysis, in environmental radioactive measurements, domestic computations and activity measurements 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 131 I and 133 Xe using a calibrated and high resolution semiconductor detector.

EXPERIMENTAL
Emission probabilities of X and -rays following the decay of 131 I and 133 Xe were measured with the experimental arrangement shown in Figure 1.The -ray and X-ray intensity measurements were performed using a Si(Li) detector with an active area of 12.5 mm 2 , a sensitive crystal depth of 3 mm and Be window of 0.025 mm thickness.The measured energy resolution of the detector system was 160 eV FWHM for the Mn K α 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 cylindrical 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 131 I and 133 Xe sources in solution.The sources in a glass tube were prepared by putting a radioactive solution containing 1,169 MBq of 131 I or 4.810 MBq for 133 Xe (the purity of the 131 I exceeded 98.9% and 133 Xe exceeded 99.5%).The solution for 131 I contains copper sulphate pentahydrate (CuSO 4 .5H 2 O), ammonium dihdrogen phosphate ((NH 4 ) 2 HPO 4 ), sodium chloride (NaCl), benzyl alcohol (C 6 H 5 CH 2 OH) and water.Otherwise, the solution for 133 Xe 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 131 I and 133 Xe are given in Figure 2. The numbers of counts in the X and -ray peaks of the spectra were determined by fitting a convolution of a Lorentzian 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 background spectrum without the sources was stripped from the spectrum acquired over the same time interval and under the same experimental conditions.

RESULTS AND DISCUSSIONS
The emission probabilities of the principal X and -rays obtained from these measurements as well as previously measured and calculated values are given in Table 1.The X and -ray emission probabilities were de- where i C E relating to the effects coincidence 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 131 I and 133 Xe are compared with previously published values as shown in Table 1.It is clear from Table 1 that the present experimental results are in general agreement with in the literature 10-12 except for the L l X-ray at 3.63 keV of Xe decay product and the γ-ray at 722.91 keV for 131 I.The Cs K 3 and Cs K 1 lines following the decay of 133 Xe 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 K 2 and Xe K 1 lines following the decay of 131 I would be discussed, the data are given separately in the Table 1.However, the closeness of there means that the uncertainties of the calculated peak areas are high.Also, in order to obtain good statistics, many of the counting times were comparable with the 131 I and 133 Xe half lives, so decay correction over the counting times was crucial.As a consequence, the discrepancies between the present measurements and previously published values of emission probabilities are within the experimental uncertainties.

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 131 I and 133 Xe.The values tabulated here can be utilized application in the analysis of nuclear materials, in nuclear medicine, 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/cm 2 and β is the self absorption correction factor given by where μ(E 0 ) and μ Ki (E) are the attenuation coefficients (cm 2 /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 θ 1 and θ 2 were equal to 45° in the present setup.
Emission probabilities for K and L X and -rays emitted in the radioactive disintegration processes were calculated by using the equation 1.When we compared the calculated K and L X and -rays emission probabilities for 131 I and 133 Xe with the measured data, as well as with previously published results, and an agreement within 0.8% to 4.8% was observed 10-12.
rate in the peak corresponding 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 131 I the activity = (1.17 0.04) MBq and 133 Xe the activity = (4.81 0.3) MBq], and   i C E is the correction factor.The correction factors  

Figure 2 .
Figure 2. Two representative spectra of K, L X-rays and -rays emitted obtained from a Si(Li) detector.

Table 1 .
Emission probabilities of X and -rays following 131 I and 133 Xe decays.