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Measurement of K-shell fluorescence yields for Br and I compounds using radioisotope XRF
Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
www.elsevier.com/locate/jqsrt
Measurement of K-shell *uorescence yields for Br and I compounds using radioisotope XRF O. Soguta; ∗ , A. K3uc4 u3 k3ondera , E. B3uy3ukkasapb , E. K3uc4 u3 k3ondera , B.G. Durdua , H. C4ama Faculty of Art and Sciences, Department of Physics, 46100 Kahramanmaras, Turkey K.S.U., Ataturk University, K.K. Education Faculty, Department of Physics Education, 25240 Erzurum, Turkey a
b
Received 31 December 2001; accepted 14 March 2002
Abstract K *uorescence yields were measured for I and Br compounds. The samples were excited by -rays 59:5 keV produced by a Am-241 radioisotope source. The K X-rays emitted by the samples were counted using a Si(Li) detector with a resolution of 155 eV at 5:9 keV. Experimental results were compared with the theoretical values of Br and I elements. ? 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction The K-shell *uorescence yield !K of an atom and ion is deCned as the probability that a vacancy in the K shell is the ratio Clled through a radiative transition and not by a radiationless transition. The K-shell *uorescence yield !K is measured by the ratio of total emission of characteristic K X-ray photons and the production of primary K-shell vacancies. Fluorescence yield values play an important role in a variety of Celds such as atomic physics, X-ray *uorescence analysis, health physics and industry. The excitation of an atom with an inner shell K vacancy result the emission of X-rays or the ejection of Auger electrons (from radiationless transition). The K-shell *uorescence yield is also deCned as the probability that one K hole is Clled through as radiative electron transition and is equal to the ratio of the total X-ray emission rate to the total decay rate: !K =
SKRad
SKRad + SKAuger
;
∗
Corresponding author. E-mail address: [email protected] (O. Sogut).
0022-4073/02/$ - see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 2 - 4 0 7 3 ( 0 2 ) 0 0 0 4 1 - 9
(1)
18
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
where SKRad and SKAuger are the total radiative and Auger transition rates, respectively. The *uorescence yield lies between 0 and 1. For low atomic number elements, Auger decay rate is larger than X-ray emission. For high atomic number elements, X-ray emission become more probable. Auger transition probability increase with decreasing binding energies of the outer shell electrons. The chemical effects are observed as diKerences in the X-ray and Auger transition probabilities from a given element incorporated in diKerent chemical compounds. K-shell *uorescence yields for diKerent elements have been investigated for many years and have been compiled by Krause [1], Bambynek et al. [2,3] and by Hubbell et al. [4,5]. Al Nasr et al. and Balakrishna et al. measured K-shell *uorescence yields for rare-earth and heavy elements [6,7]. Durak et al. [8–10] reported experimental K-shell *uorescence yields for diKerent elements, in the atomic range 40 6 Z 6 82. Theoretical values of !K were obtained for various elements by McGuire [11,12], Walters and Bhalla [13], Kastroun et al. [14] and Chen et al. [15] by using diKerent approaches. B3uy3ukkasap [16] investigated K-shell *uorescence yield in Cr and Ni alloys. Although chemical eKects on K X-ray intensity ratios have been studied by some workers, there are not any studies addressing chemical eKects on K X-ray *uorescence yield. This is Crst analytical investigation of K X-ray *uorescence yield on chemical eKects. In this paper, K X-ray *uorescence yield for Br and I compounds were investigated. Br and I are halogens and, in the nature, the halogens normally occur in compounds form.
2. Experimental Experimental measurements were carried out on K characteristic radiations stimulated 59:5 keV -photons of 75 mCi 241 Am source for Br and I compounds. The purity of commercially obtained materials was better than 99%. All of samples were sieved using 400 Mesh-powder samples of (34 × 10−3 ) g cm2 thickness and 3:4 cm diameter were prepared by using the sample preparation cylindrical cup and rod produced in our research laboratory and supported on mylar Clm. The experimental geometry is shown in Fig. 1. As shown in Cgure, the L X-rays from lead shields were hold by Cu shield in order to prevent them from reaching the detector. X-rays emitted from the samples were detected by a Si(Li) detector (FWHM = 155 eV at 5:9 keV). Two typical K X-ray spectra obtained from KBrO3 and NaBr are comparatively given in Fig. 2. The background was measured by using the calculation of mean of a ten-channel approximation. Then the net peak area was found out by subtraction of the background from the total peak area. K-shell *uorescence yields !K determined using the following equation semiempirically !K =
K ;K ; KPhoto
(2)
where K ;K is the total K X-ray *uorescence cross-section and KPhoto is the K-shell photoionization cross-section [17]. Experimental K and K X-ray *uorescence cross-sections were measured using the equation Ki =
NKi ; I0 GKi Tt
(3)
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
19
Fig. 1. Experimental geometry.
4000
3000 Count
Count
3000 Kα
2000 1000 0 810
NaBr
Kα
4000
KBrO3
870
900
Channel
930
960
Kβ
1000
Kβ
840
2000
990
0 810
840
870
900
930
960
990
Channel
Fig. 2. Characteristic K X-ray emission spectra of KBrO3 and NaBr.
where NKi (i = ; ) is intensity observed for Ki (i = ; ) X-ray line of element. Ki is the detector eRciency for Ki X-rays, I0 is the intensity of exciting radiation, G is the geometrical factor, t is the mass of the sample in g cm−2 and T is self-absorption correction factor of the target material. The self-absorption correction factor has been calculated by using the following expression
20
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
obtained by assuming the incidence angle of the *uorescent X-rays subtended at the detector to be ◦ approximately 90 : T=
1 − exp[(−1)((inc) =cos + (emt) )t] ; ((inc) =cos + (emt) )t
(4)
where (inc) (cm2 g−1 ) and (emt) (cm2 g−1 ) are mass absorption coeRcients [18] at the incident photon energy and *uorescent X-ray energy of sample, respectively, t (g cm−2 ) is the measured thickness of sample. I0 GKi values in the present experimental set-up were determined in a separate experiment. Targets of pure elements, having areas of cross-section similar to those used in the main experiment, with atomic number 30 6 Z 6 58, emitting *uorescent radiation in energy range 8.5 –40 keV were irradiated in same geometry and *uorescent radiation were counted. I0 GKi values for the present set-up were determined by the following relation ship: I0 GKi =
NK i ; Ki Tt
(5)
where NKi is the number of counts under the K or K peaks, Ki is the K or K *uorescence cross-section.
3. Results and discussion K-shell *uorescence yields were measured for various Br and I chemical compounds and were compared with theoretical values of Br and I elements [1,4,19]. The errors in the present measurement are due to I0 G determination 2%, counting statistic for K and K peaks 0.7–2.8%, target thickness measurement 2% and self absorption correction 2%. We could not make any comparison of results of Br and I compounds since there are not experimental and theoretical values for Br and I compounds in literature. Br and I are halogens and, in nature, the halogens normally occur in compound form. The electronic conCgurations of Br and I are 3d 10 4s2 4p5 and 4d 10 5s2 5p5 , respectively. Electron aRnities and electronegativities of the halogens (Br and I) are larger than those of the other elements. According to the results shown in Table 1, K-shell *uorescence yield of Br and I compounds depend on chemical eKects. Chemical eKects on the K-shell *uorescence yield for Br compounds are larger than I compounds because the ionic character of I compounds is less than that of Br compounds. As seen from Table 1, molecules have diKerent bond energies and diKerent interatomic bond dictances between ligands and central atom. DiKerent interatomic bond distances cause diKerent interaction between ligands and central atoms. This eKects play an important role in K X-ray transitions. An increase in K-shell *uorescence yield are observed with increasing interatomic distances. Chemical bonding type (ionic, metalic, covalent) aKects the K-shell *uorescence yield. The individual characteristic of the structure of molecules, complexes and crystals (polarity valency and electronegativity of atoms, coordination number, ionicities of covalent bond, etc.) mainly aKect the K-shell *uorescence yield. A change in chemical bond leads to a change in its valence electron density. The electron density decreases or increases depending on the type of bonding with adjacent atoms in molecule or crystal.
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
21
Table 1 K-shell *uorescence yield
Compounds
Br Br 2 C21 H16 Br 2 O5 S C7 H5 O2 Br KBrO3 C6 H6 BrN C19 H10 Br 4 S KBr NaBr NH4 Br I NH4 I I2 NaIO3 Hg2 I2 KI KIO3
Experimental
— — 0:325 ± 0:014 0:426 ± 0:013 0:536 ± 0:013 0:572 ± 0:011 0:579 ± 0:011 0:724 ± 0:011 0:787 ± 0:015 0:892 ± 0:018 0:845 ± 0:025 0:886 ± 0:028 0:932 ± 0:029 0:980 ± 0:032 0:983 ± 0:026 0:990 ± 0:028
Theoretical
Interatomic S distances (A)
Krause [1]
Broll [19]
Hubbell [4]
0.618 — — — — — — — — — 0.884 — — — — — —
0.630 — — — — — — — — — 0.880 — — — — — —
0.6275 — — — — — — — — — 0.8819 — — — — — —
— 2.29 — — 2.94 — — 3.30 2.98 — — — 2.66 3.16 — 3.53 —
References [1] Krause MO. J Phys Chem Ref Data 1979;8:307. [2] Bambynek W, Crasemann B, Fink RW, Freund HU, Mark H, Swift CD, Price RE, Rao PV. Rev Mod Phys 1972;44:176. [3] Bambynek W. X-84 Proceedings of X Ray and Inner Shell Processes in Atoms, Molecules and Solids, Leipzig, August 20 –23, 1984. [4] Hubbell JH. NISTIR 89-4144, 1989. [5] Hubbell JH, Trehan PN, Singh N, Chand B, Mehta D, Garg ML, Garg RR, Singh S, Puri S. J Phys Chem Ref Data 1994;23:339. [6] Al-Nasr IA, Jabr IJ, AL-Saleh KA, Saleh NS. Appl Phys A 1987;43:71. [7] Balakrishna KM, Nayak N, Lingappa N, Siddappa K. J Phys B At Mol Opt Phys B 1994;27:715. [8] Durak RS4, ahin Y. Nucl Instrum Methods B 1997;124:1. [9] Durak RS4, ahin Y. Phys Rev A 1998;57:4. [10] Durak R. Phys Scr 1998;58:111. [11] McGuire EJ. Phys Rev 1969;185:1. [12] McGuire EJ. Phys Rev A 1970;273:2. [13] Walters DL, Bhalla CP. Phys Rev A 1971;3:1919. [14] Kostroun VO, Chen MH, Crasemann B. Phys Rev A 1971;3:533. [15] Chen MH, Crasemann B, Mark H. Phys Rev A 1980;21:436. [16] B3uy3ukkasap E. Spectrochim Acta B 1998;53:499. [17] ScoCeld JH, Report UCRL 51326, Livermore CA: Lawrence Livermore Laboratory, 1973. [18] Hubbell JH, Seltzer SM, National Institute of Standards and Technology Physics Laboratory Ionizing Radiation Division, Gaithersburg, Report No. NISTIR 5692, 1995. [19] Broll N. X-Ray Spectrometry 1986;15:271–85.
www.elsevier.com/locate/jqsrt
Measurement of K-shell *uorescence yields for Br and I compounds using radioisotope XRF O. Soguta; ∗ , A. K3uc4 u3 k3ondera , E. B3uy3ukkasapb , E. K3uc4 u3 k3ondera , B.G. Durdua , H. C4ama Faculty of Art and Sciences, Department of Physics, 46100 Kahramanmaras, Turkey K.S.U., Ataturk University, K.K. Education Faculty, Department of Physics Education, 25240 Erzurum, Turkey a
b
Received 31 December 2001; accepted 14 March 2002
Abstract K *uorescence yields were measured for I and Br compounds. The samples were excited by -rays 59:5 keV produced by a Am-241 radioisotope source. The K X-rays emitted by the samples were counted using a Si(Li) detector with a resolution of 155 eV at 5:9 keV. Experimental results were compared with the theoretical values of Br and I elements. ? 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction The K-shell *uorescence yield !K of an atom and ion is deCned as the probability that a vacancy in the K shell is the ratio Clled through a radiative transition and not by a radiationless transition. The K-shell *uorescence yield !K is measured by the ratio of total emission of characteristic K X-ray photons and the production of primary K-shell vacancies. Fluorescence yield values play an important role in a variety of Celds such as atomic physics, X-ray *uorescence analysis, health physics and industry. The excitation of an atom with an inner shell K vacancy result the emission of X-rays or the ejection of Auger electrons (from radiationless transition). The K-shell *uorescence yield is also deCned as the probability that one K hole is Clled through as radiative electron transition and is equal to the ratio of the total X-ray emission rate to the total decay rate: !K =
SKRad
SKRad + SKAuger
;
∗
Corresponding author. E-mail address: [email protected] (O. Sogut).
0022-4073/02/$ - see front matter ? 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 2 - 4 0 7 3 ( 0 2 ) 0 0 0 4 1 - 9
(1)
18
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
where SKRad and SKAuger are the total radiative and Auger transition rates, respectively. The *uorescence yield lies between 0 and 1. For low atomic number elements, Auger decay rate is larger than X-ray emission. For high atomic number elements, X-ray emission become more probable. Auger transition probability increase with decreasing binding energies of the outer shell electrons. The chemical effects are observed as diKerences in the X-ray and Auger transition probabilities from a given element incorporated in diKerent chemical compounds. K-shell *uorescence yields for diKerent elements have been investigated for many years and have been compiled by Krause [1], Bambynek et al. [2,3] and by Hubbell et al. [4,5]. Al Nasr et al. and Balakrishna et al. measured K-shell *uorescence yields for rare-earth and heavy elements [6,7]. Durak et al. [8–10] reported experimental K-shell *uorescence yields for diKerent elements, in the atomic range 40 6 Z 6 82. Theoretical values of !K were obtained for various elements by McGuire [11,12], Walters and Bhalla [13], Kastroun et al. [14] and Chen et al. [15] by using diKerent approaches. B3uy3ukkasap [16] investigated K-shell *uorescence yield in Cr and Ni alloys. Although chemical eKects on K X-ray intensity ratios have been studied by some workers, there are not any studies addressing chemical eKects on K X-ray *uorescence yield. This is Crst analytical investigation of K X-ray *uorescence yield on chemical eKects. In this paper, K X-ray *uorescence yield for Br and I compounds were investigated. Br and I are halogens and, in the nature, the halogens normally occur in compounds form.
2. Experimental Experimental measurements were carried out on K characteristic radiations stimulated 59:5 keV -photons of 75 mCi 241 Am source for Br and I compounds. The purity of commercially obtained materials was better than 99%. All of samples were sieved using 400 Mesh-powder samples of (34 × 10−3 ) g cm2 thickness and 3:4 cm diameter were prepared by using the sample preparation cylindrical cup and rod produced in our research laboratory and supported on mylar Clm. The experimental geometry is shown in Fig. 1. As shown in Cgure, the L X-rays from lead shields were hold by Cu shield in order to prevent them from reaching the detector. X-rays emitted from the samples were detected by a Si(Li) detector (FWHM = 155 eV at 5:9 keV). Two typical K X-ray spectra obtained from KBrO3 and NaBr are comparatively given in Fig. 2. The background was measured by using the calculation of mean of a ten-channel approximation. Then the net peak area was found out by subtraction of the background from the total peak area. K-shell *uorescence yields !K determined using the following equation semiempirically !K =
K ;K ; KPhoto
(2)
where K ;K is the total K X-ray *uorescence cross-section and KPhoto is the K-shell photoionization cross-section [17]. Experimental K and K X-ray *uorescence cross-sections were measured using the equation Ki =
NKi ; I0 GKi Tt
(3)
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
19
Fig. 1. Experimental geometry.
4000
3000 Count
Count
3000 Kα
2000 1000 0 810
NaBr
Kα
4000
KBrO3
870
900
Channel
930
960
Kβ
1000
Kβ
840
2000
990
0 810
840
870
900
930
960
990
Channel
Fig. 2. Characteristic K X-ray emission spectra of KBrO3 and NaBr.
where NKi (i = ; ) is intensity observed for Ki (i = ; ) X-ray line of element. Ki is the detector eRciency for Ki X-rays, I0 is the intensity of exciting radiation, G is the geometrical factor, t is the mass of the sample in g cm−2 and T is self-absorption correction factor of the target material. The self-absorption correction factor has been calculated by using the following expression
20
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
obtained by assuming the incidence angle of the *uorescent X-rays subtended at the detector to be ◦ approximately 90 : T=
1 − exp[(−1)((inc) =cos + (emt) )t] ; ((inc) =cos + (emt) )t
(4)
where (inc) (cm2 g−1 ) and (emt) (cm2 g−1 ) are mass absorption coeRcients [18] at the incident photon energy and *uorescent X-ray energy of sample, respectively, t (g cm−2 ) is the measured thickness of sample. I0 GKi values in the present experimental set-up were determined in a separate experiment. Targets of pure elements, having areas of cross-section similar to those used in the main experiment, with atomic number 30 6 Z 6 58, emitting *uorescent radiation in energy range 8.5 –40 keV were irradiated in same geometry and *uorescent radiation were counted. I0 GKi values for the present set-up were determined by the following relation ship: I0 GKi =
NK i ; Ki Tt
(5)
where NKi is the number of counts under the K or K peaks, Ki is the K or K *uorescence cross-section.
3. Results and discussion K-shell *uorescence yields were measured for various Br and I chemical compounds and were compared with theoretical values of Br and I elements [1,4,19]. The errors in the present measurement are due to I0 G determination 2%, counting statistic for K and K peaks 0.7–2.8%, target thickness measurement 2% and self absorption correction 2%. We could not make any comparison of results of Br and I compounds since there are not experimental and theoretical values for Br and I compounds in literature. Br and I are halogens and, in nature, the halogens normally occur in compound form. The electronic conCgurations of Br and I are 3d 10 4s2 4p5 and 4d 10 5s2 5p5 , respectively. Electron aRnities and electronegativities of the halogens (Br and I) are larger than those of the other elements. According to the results shown in Table 1, K-shell *uorescence yield of Br and I compounds depend on chemical eKects. Chemical eKects on the K-shell *uorescence yield for Br compounds are larger than I compounds because the ionic character of I compounds is less than that of Br compounds. As seen from Table 1, molecules have diKerent bond energies and diKerent interatomic bond dictances between ligands and central atom. DiKerent interatomic bond distances cause diKerent interaction between ligands and central atoms. This eKects play an important role in K X-ray transitions. An increase in K-shell *uorescence yield are observed with increasing interatomic distances. Chemical bonding type (ionic, metalic, covalent) aKects the K-shell *uorescence yield. The individual characteristic of the structure of molecules, complexes and crystals (polarity valency and electronegativity of atoms, coordination number, ionicities of covalent bond, etc.) mainly aKect the K-shell *uorescence yield. A change in chemical bond leads to a change in its valence electron density. The electron density decreases or increases depending on the type of bonding with adjacent atoms in molecule or crystal.
O. Sogut et al. / Journal of Quantitative Spectroscopy & Radiative Transfer 76 (2003) 17 – 21
21
Table 1 K-shell *uorescence yield
Compounds
Br Br 2 C21 H16 Br 2 O5 S C7 H5 O2 Br KBrO3 C6 H6 BrN C19 H10 Br 4 S KBr NaBr NH4 Br I NH4 I I2 NaIO3 Hg2 I2 KI KIO3
Experimental
— — 0:325 ± 0:014 0:426 ± 0:013 0:536 ± 0:013 0:572 ± 0:011 0:579 ± 0:011 0:724 ± 0:011 0:787 ± 0:015 0:892 ± 0:018 0:845 ± 0:025 0:886 ± 0:028 0:932 ± 0:029 0:980 ± 0:032 0:983 ± 0:026 0:990 ± 0:028
Theoretical
Interatomic S distances (A)
Krause [1]
Broll [19]
Hubbell [4]
0.618 — — — — — — — — — 0.884 — — — — — —
0.630 — — — — — — — — — 0.880 — — — — — —
0.6275 — — — — — — — — — 0.8819 — — — — — —
— 2.29 — — 2.94 — — 3.30 2.98 — — — 2.66 3.16 — 3.53 —
References [1] Krause MO. J Phys Chem Ref Data 1979;8:307. [2] Bambynek W, Crasemann B, Fink RW, Freund HU, Mark H, Swift CD, Price RE, Rao PV. Rev Mod Phys 1972;44:176. [3] Bambynek W. X-84 Proceedings of X Ray and Inner Shell Processes in Atoms, Molecules and Solids, Leipzig, August 20 –23, 1984. [4] Hubbell JH. NISTIR 89-4144, 1989. [5] Hubbell JH, Trehan PN, Singh N, Chand B, Mehta D, Garg ML, Garg RR, Singh S, Puri S. J Phys Chem Ref Data 1994;23:339. [6] Al-Nasr IA, Jabr IJ, AL-Saleh KA, Saleh NS. Appl Phys A 1987;43:71. [7] Balakrishna KM, Nayak N, Lingappa N, Siddappa K. J Phys B At Mol Opt Phys B 1994;27:715. [8] Durak RS4, ahin Y. Nucl Instrum Methods B 1997;124:1. [9] Durak RS4, ahin Y. Phys Rev A 1998;57:4. [10] Durak R. Phys Scr 1998;58:111. [11] McGuire EJ. Phys Rev 1969;185:1. [12] McGuire EJ. Phys Rev A 1970;273:2. [13] Walters DL, Bhalla CP. Phys Rev A 1971;3:1919. [14] Kostroun VO, Chen MH, Crasemann B. Phys Rev A 1971;3:533. [15] Chen MH, Crasemann B, Mark H. Phys Rev A 1980;21:436. [16] B3uy3ukkasap E. Spectrochim Acta B 1998;53:499. [17] ScoCeld JH, Report UCRL 51326, Livermore CA: Lawrence Livermore Laboratory, 1973. [18] Hubbell JH, Seltzer SM, National Institute of Standards and Technology Physics Laboratory Ionizing Radiation Division, Gaithersburg, Report No. NISTIR 5692, 1995. [19] Broll N. X-Ray Spectrometry 1986;15:271–85.